1. Introduction
We wrote this article to familiarize ourselves (and the reader) with the definition of compactly supported p-adic pro-étale cohomology of smooth partially proper rigid analytic varieties, to study its basic properties, and to present some computations. This article should be thought of as a compactly supported counterpart of the series [Reference Colmez and Nizioł14], [Reference Colmez and Nizioł15], [Reference Colmez and Nizioł16] but, in particular, as a continuation of [Reference Colmez and Nizioł15].
Let K be a complete discrete valuation field of characteristic 0 with a perfect residue field k of characteristic p. Let C be the p-adic completion of an algebraic closure of K. Let
${\mathscr {G}}_K$
be the Galois group of K. Let
$F={\mathrm Frac}(W(k))$
and let
$\varphi $
be the absolute Frobenius on
$W(\overline {k})$
.
1.1. Definitions
The study of p-adic étale cohomology of analytic varieties over C is a relatively recent endeavor. It started in earnest with [Reference Scholze28], where Scholze proved, among other things, finiteness of p-adic étale cohomology of proper rigid analytic varieties. For compactly supported p-adic pro-étale cohomology of smooth partially proper varieties, it was not clear initially what the right definitions should be. There were two immediate guesses:
where
$\Phi _X$
denotes the set of quasi-compact opens in X, and the brackets
$[\dots ]$
denote the mapping fiber. The first definition is just a continuous version of
$\mathbf {Z}/p^n$
-cohomology. The heuristic for the second definition comes from the (possible) comparison with de Rham cohomology and the classical definition of van der Put of compactly supported version of the latter [Reference van der Put30]. It came to us as a surprise that this definition agrees with Huber’s definition of compactly supported p-adic étale (sic!) cohomology (see Theorem 1.2 below): this follows from the canonical quasi-isomorphism
The fact that this might be the right definition comes from the work on dualities which pairs this cohomology with p-adic pro-étale cohomology (see [Reference Anschütz, Le Bras and Mann1], [Reference Colmez, Gilles and Nizioł10], [Reference Colmez, Gilles and Nizioł11], [Reference Li23]). Hence, we set
We note that, if we take étale instead of pro-étale in the first definition of (1.1), we obtain an isomorphic object. The indication that this is actually a good definition of compactly supported p-adic étale cohomology (sic!) comes from two sources:
-
1. In [Reference Colmez, Dospinescu, Hauseux and Nizioł9], it was shown that, for p-adic period domains, it behaves like $\ell $
-adic cohomology for
$\ell \neq p$
. -
2. In [Reference Lan, Liu and Zhu22], it was shown that, for smooth almost proper varieties (i.e., $X=\overline {X}\setminus Z$
, for a smooth proper variety
$\overline {X}$
and a closed Zariski subvariety Z), it satisfies Poincaré duality vis-à-vis p-adic étale cohomology.
Hence, we set
It is a nonobvious fact but there exists a canonical map
$\mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} ,c}(X,\mathbf {Q}_p)\to \mathrm {R}\Gamma _{\mathrm {\acute {e}t} ,c}(X,\mathbf {Q}_p)$
.
1.2. Main results
The main result of the article can be summed up in the following theorem-construction. We write
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
for the
$\infty $
-derived category of solid
$\mathbf {Q}_p$
-modules and
${\mathscr {F}}{\mathscr {D}}(\mathbf {Q}_{p,\Box })$
for the corresponding filtered
$\infty $
-derived category.
Theorem 1.2. To any smooth partially proper rigid analytic variety X over C, there are naturally associated:
-
1. The pro-étale cohomology with compact support $ \mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} ,c}(X,\mathbf {Q}_p)\in {\mathscr {D}}(\mathbf {Q}_{p,\Box })$
. There is a natural quasi-isomorphism in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
with Huber’s étale cohomology with compact support (1.3) $$ \begin{align} \mathrm{R}\Gamma_{\mathrm{pro\acute{e}t} ,c}(X,\mathbf{Q}_p)\simeq \mathrm{R}\Gamma_{\mathrm{\acute{e}t} ,c, \mathrm{Hu}}(X,\mathbf{Q}_p). \end{align} $$
-
2. The syntomic cohomology with compact support $\mathrm {R}\Gamma _{ \mathrm {syn} ,c}(X,\mathbf {Q}_p(r))\in {\mathscr {D}}(\mathbf {Q}_{p,\Box })$
,
$r\in \mathbf {N}$
, with a natural period morphism in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
(1.4) $$ \begin{align} \alpha_r: \mathrm{R}\Gamma_{ \mathrm{syn} ,c}(X,\mathbf{Q}_p(r))\to \mathrm{R}\Gamma_{\mathrm{pro\acute{e}t} ,c}(X,\mathbf{Q}_p(r)), \end{align} $$which is a quasi-isomorphism after truncation $\tau _{\leq r}$
.
-
3. The de Rham cohomology $\mathrm {R}\Gamma _{\mathrm {dR} ,c}(X)$
and
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology
$\mathrm {R}\Gamma _{\mathrm {dR} ,c}(X/{\mathbf B}^+_{\mathrm {dR} })$
. These are filtered dg C- and
${\mathbf B}^+_{\mathrm {dR} }$
-algebras, respectively, such that, in
${\mathscr {F}}{\mathscr {D}}(\mathbf {Q}_{p,\Box }),$
$$ \begin{align*}\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} })\otimes^{\mathrm{L}_{\Box}}_{{\mathbf B}^+_{\mathrm{dR} }}C\stackrel{\sim}{\to}\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X). \end{align*} $$
-
4. The Hyodo–Kato cohomology $\mathrm {R}\Gamma _{\mathrm {HK} ,c}(X)$
. This is a dg
$F^{\mathrm {nr} }$
-algebraFootnote
1
equipped with a Frobenius
$\varphi $
and a monodromy operator N. We have
$:$
-
(a) Natural Hyodo–Kato quasi-isomorphisms in ${\mathscr {D}}(C_{\Box })$
and
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
, respectively
$:$
$$ \begin{align*} \iota_{\mathrm{HK} } &: \mathrm{R}\Gamma_{\mathrm{HK} ,c}(X){\otimes}^{\mathrm{L}_{\Box}}_{F^{\mathrm{nr} }}C\stackrel{\sim}{\to} \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X);\\ \iota_{\mathrm{HK} }&: \mathrm{R}\Gamma_{\mathrm{HK} ,c}(X){\otimes}^{\mathrm{L}_{\Box}}_{F^{\mathrm{nr} }}{\mathbf B}^+_{\mathrm{dR} }\stackrel{\sim}{\to} \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} }). \end{align*} $$
-
(b) (Poincaré duality) If X is everywhere of dimension d, then the natural pairing of solid $(\varphi ,N)$
-modules over
$F^{\mathrm {nr}}$
$$ \begin{align*}H^i_{\mathrm{HK} }(X)\otimes^{\Box}_{F^{\mathrm{nr} }} H^{2d-i}_{\mathrm{HK} ,c}(X)\stackrel{\cup}{\to} H^{2d}_{\mathrm{HK} ,c}(X)\xrightarrow{{\mathrm tr}_{\mathrm{HK} }} F^{\mathrm{nr}}\{-d\} \end{align*} $$
is a perfect duality, that is, we have induced isomorphisms of solid $(\varphi ,N)$
-modules over
$F^{\mathrm {nr}}$
$$ \begin{align*} & H^i_{\mathrm{HK} }(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{F^{\mathrm{nr}}_{\Box}} (H^{2d-i}_{\mathrm{HK} ,c}(X),F^{\mathrm{nr}}\{-d\}),\\ & H^i_{\mathrm{HK} ,c}(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{F^{\mathrm{nr}}_{\Box}} (H^{2d-i}_{\mathrm{HK} }(X),F^{\mathrm{nr}}\{-d\}). \end{align*} $$
These duality isomorphisms are compatible, via the Hyodo–Kato isomorphism, with the de Rham duality.
-
-
5. A distinguished triangle in ${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
(1.5)which can be lifted to the derived category of topological vector spaces.![R Gamma syn,c (X, Q sub p (r)) maps to [R Gamma H K,c (X) tensor product over F super nr with B sub st super +] super N=0, phi=p super r which maps via iota H K to R Gamma d R,c (X / B sub d R super +) / F super r](data:image/gif;base64,R0lGODlhAQABAIAAAMLCwgAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==)
-
6. (Trace maps) If X is of dimension d and irreducible, the syntomic trace map induces, via (1.4), a natural trace map
$$ \begin{align*}{\mathrm tr}_{\mathrm{pro\acute{e}t} ,X}: H^{2d}_{\mathrm{pro\acute{e}t} ,c}(X,\mathbf{Q}_p(d))\to \mathbf{Q}_p, \end{align*} $$which is compatible with Berkovich’s trace map (via (1.3)).
Some of the constructions in the above theorem follow in a rather straightforward, if technically tedious,Footnote 2 manner from the ones for usual cohomologies. Others, like the comparison with Huber’s definition, the definition of the trace maps, the Poincaré duality for Hyodo–Kato cohomology, and the related computations require subtler arguments. The duality for Hyodo–Kato cohomology is induced from the one for de Rham cohomology (a classical result) but the information about Frobenius and monodromy (as well as Galois action if needed) is obtained by a reduction (via excision) to the proper case. The pro-étale trace map is defined by passing to the syntomic cohomology via period quasi-isomorphism and then using the Hyodo–Kato trace map (via the distinguished triangle (1.5)). That it agrees with Berkovich’s trace map can be checked by a reduction to the algebraic case (again, via excision) where this amounts to the compatibility of the algebraic p-adic comparison morphism with traces.
From Theorem 1.2, we derive the following key result.
Corollary 1.6. Let
$X_C$
be a smooth partially proper rigid analytic variety over C.
-
1. (Basic comparison theorem) Let $r\geq 0$
. There is a natural quasi-isomorphism (period isomorphism) in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
: (1.7)![tau sub less than or equal to r R Gamma proet,c (X sub C, Q sub p (r)) is isomorphic to tau sub less than or equal to r [R Gamma HK,c (X sub C) tensor L square over F nr B st super +] N=0, phi=p^r arrow i HK R Gamma dR,c (X sub C / B dR super +) / F^r](data:image/gif;base64,R0lGODlhAQABAIAAAMLCwgAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==)
-
2. (Fundamental diagram) If $X_C=X\times _KC$
, for a Stein variety X of dimension d over K and
$r\geq 0$
, then, if the Hyodo–Kato cohomology
$H^{r-1}_{\mathrm {HK} ,c}(X_C)$
is pure of Frobenius slope
$r-1-d$
, there is a map of exact sequences of solid
$\mathbf {Q}_p$
-modules 
where we set
.
The Frobenius slope condition above is very restrictive but it holds for tori and Drinfeld spaces, for example, so we can use the fundamental diagram to compute compactly supported cohomology in these cases. Recall that, for the usual cohomology, we have a fundamental diagram with no restrictions on the slopes.Footnote 3
Finally, the article includes a number of concrete examples of computations of compactly supported p-adic pro-étale cohomology: Drinfeld spaces and tori (already mentioned above) but also affine spaces, Stein curves, and general Stein spaces (the last one—up to a degree).
-
1. We also prove analogs of Theorem 1.2 and Corollary 1.6 for smooth overconvergent varieties and compare them with their rigid analytic versions as in [Reference Colmez and Nizioł15]. Here, again, it was not clear what should be the right definition of compactly supported p-adic pro-étale cohomology of an overconvergent variety and our definition is inspired, as in the rigid analytic case, by the definition of compactly supported de Rham cohomology of dagger affinoids of Grosse-Klönne from [Reference Grosse-Klönne18].
-
2. For a further study of properties of compactly supported p-adic cohomologies of rigid analytic spaces, see the work of Shao [Reference Shao29]. For a formulation of $C_{\mathrm {st} }$
conjecture in the same context, see the work of Colmez et al. [Reference Colmez, Gilles and Nizioł12].
Notation and conventions. Let
${\mathscr O}_K$
be a complete discrete valuation ring with fraction field K of characteristic 0 and with perfect residue field k of characteristic p. Let
$\overline {K} $
be an algebraic closure of K and let
${\mathscr O}_{\overline {K} }$
denote the integral closure of
${\mathscr O}_K$
in
$\overline {K} $
. Let
$C=\widehat {\overline {K} }$
be the p-adic completion of
$\overline {K} $
. Let
$W(k)$
be the ring of Witt vectors of k with fraction field F (i.e.,
$W(k)={\mathscr O}_F$
); let
$e=e_K$
be the ramification index of K over F. Set
${\mathscr {G}}_K=\mathrm {Gal} (\overline {K}/K)$
and let
$\varphi $
be the absolute Frobenius on
$W(\overline {k})$
. We will denote by
${\mathbb A}_{\mathrm {cr} }, {\mathbf B}_{\mathrm {cr} }, {\mathbf B}_{\mathrm {st} },{\mathbf B}_{\mathrm {dR} }$
the crystalline, semistable, and de Rham period rings of Fontaine.
We will denote by
${\mathscr O}_K$
,
${\mathscr O}_K^{\times }$
, and
${\mathscr O}_K^0$
, depending on the context, the scheme
$\mathrm {Spec} ({{\mathscr O}_K})$
or the formal scheme
$\mathrm {Spf} ({\mathscr O}_K)$
with the trivial, the canonical (i.e., associated with the closed point), and the induced by
$\mathbf {N}\to {\mathscr O}_K, 1\mapsto 0$
, log-structure, respectively. Unless otherwise stated, all formal schemes are p-adic, locally of finite type, and equidimensional. For a (p-adic formal) scheme X over
${\mathscr O}_K$
, let
$X_0$
denote the special fiber of X; let
$X_n$
denote its reduction modulo
$p^{n+1}$
.
All rigid analytic spaces considered will be over K or C. We assume that they are separated, taut,Footnote
4
and countable at infinity. If
$L=K,C$
, we let
${\mathrm Sm}_L$
(resp.
${\mathrm Sm}_L^\dagger $
) be the category of smooth rigid analytic (resp. dagger) varieties over L, and we denote by
${\mathrm Perf}_C$
the category of perfectoid spaces over C.
Unless otherwise stated, we work in the derived (stable)
$\infty $
-category
${\mathscr {D}}(A)$
of left-bounded complexes of a quasi-abelian category A (the latter will be clear from the context). Many of our constructions will involve (pre)sheaves of objects from
${\mathscr {D}}(A)$
. We will use a shorthand for certain homotopy limits: if
$f:C\to C'$
is a map in the derived
$\infty $
-category of a quasi-abelian category, we set
For an operator F acting on C, we will use the brackets
$[C ]^F$
to denote the derived eigenspaces and the brackets
$(C)^F$
or simply
$C^F$
to denote the non-derived ones. We will also write
![Equation showing a commutative diagram in brackets defined as [ [ C sub 1 f sub 1 → K sub 1 ] → [ C sub 2 f sub 2 → K sub 2 ] ]. The diagram has C sub 1 → K sub 1 over C sub 2 → K sub 2 with vertical arrows connecting them.](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu11.png?pub-status=live)
For functional analysis, we will work in the context of condensed mathematics. We write
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
for the
$\infty $
-derived category of solid
$\mathbf {Q}_p$
-modules; (a bit abusively) we will write
$\mathbf {Q}_{p,\Box }$
for the category of solid
$\mathbf {Q}_p$
-modules. We will use similar notation for modules over a solid
$\mathbf {Q}_p$
-ring, etc.
2. Pro-étale cohomology with compact support
Let
$\ell $
be a prime number. In this section, we define compactly supported
$\ell $
-adic pro-étale cohomology for partially proper smooth rigid analytic varieties and smooth dagger varieties over K or C. This cohomology was used in [Reference Colmez, Gilles and Nizioł10] to obtain a Poincaré duality for arithmetic p-adic pro-étale cohomology of rigid analytic Stein curves.
2.1. Rigid analytic compact support functor
We start with a preliminary discussion. Let
$L= K, C$
and let X be a smooth rigid analytic variety over L. Let
$\Phi $
denote the set of quasi-compact opens of X. We write
$\partial X$
for the pro-object
$\{X\setminus Z\}_{Z\in \Phi }$
indexed by
$\Phi ^{\mathrm op}$
. We note that
$X\setminus Z$
is an admissible open of X (see [Reference van der Put30, Lemma 1.1]). For a presheaf F on smooth rigid analytic varieties with values in an
$\infty $
-category
${\mathscr {C}}$
admitting filtered colimits, we set
We have a natural restriction map
$F(X)\to F(\partial X)$
. Suppose that
${\mathscr {C}}$
is stable and set
so that we have a distinguished triangle
Note that, if X is quasi-compact, then
$\Phi $
admits a final object
$X,$
and if, moreover,
$F(\emptyset )$
is the final object, then we have
$F_c(X)\stackrel {\sim }{\to }F(X)$
.
Suppose now that F is a sheaf. Let
$U\subset X$
be an open. For every
$Z\in \Phi ,$
whose closure is contained in U, that is,
$Z\Subset _XU$
, covering X by
$X\setminus Z$
and U, we have a Cartesian square

and hence, setting
$F_Z(-):=[F(-)\to F(-\setminus Z)]$
, we get the excision
Now suppose that
$j:U\to X$
is partially proper, so that, for every quasi-compact open Z of U, the closure of Z in X is also contained in U. Letting Z run over
$\Phi _U$
(quasi-compact opens for U), we get the pushforward map
as the composition:
We used here (2.1). Clearly, the map
$j_*$
is functorial in F.
2.2. Rigid analytic setting
Following the same process as in Section 2.1, we define compactly supported (pro-)étale cohomology of a smooth rigid analytic variety X over K or C. We give the definition for torsion coefficients as well as
$\ell $
-adic ones. We show that our construction coincides with the one of Huber [Reference Huber20] in the case of partially proper varieties.
2.2.1. Definition
Let
$L=K,C$
. Let X be a smooth rigid analytic variety over L. We define compactly supported cohomology with torsion coefficients of X by the same formulas as in Section 2.1, that is,
where
$*=\mathrm {\acute {e}t} ,\mathrm {pro\acute {e}t} $
and
We then define the integral cohomologies by
We obtain complexes in
${\mathscr D}(\mathbf {Z}_{\ell ,\Box })$
.
Remark 2.2. If we define
the natural map
induces a map
$\mathrm {R} \Gamma _{\mathrm {\acute {e}t} ,c,{\mathrm naive}}(X, \mathbf {Z}_{\ell }) \to \mathrm {R} \Gamma _{\mathrm {\acute {e}t} ,c}(X, \mathbf {Z}_{\ell })$
. In general, it is not a quasi-isomorphism.
For the rational theory, we set
![Equation 1: R Gamma sub et,c (X, Q sub l) is defined as R Gamma sub et,c (X, Z sub l) tensor product over Z sub l with Q sub l. Equation 2: R Gamma sub proet,c (X, Q sub l) is defined as [R Gamma sub proet (X, Q sub l) yields R Gamma sub proet (partial X, Q sub l)].](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu23.png?pub-status=live)
These are complexes in
${\mathscr D}(\mathbf {Q}_{\ell ,\Box })$
.
-
1. The natural morphism $\mathrm {R} \Gamma _{\mathrm {\acute {e}t} ,c, {\mathrm naive}}(X, \mathbf {Z}_{\ell }) \to \mathrm {R} \Gamma _{\mathrm {pro\acute {e}t} ,c}(X, \mathbf {Z}_{\ell })$
is a quasi-isomorphism in
${\mathscr D}(\mathbf {Z}_{\ell ,\Box })$
. -
2. It induces a natural change of topology morphism in ${\mathscr D}(\mathbf {Z}_{\ell ,\Box }){:}$
(2.4) $$ \begin{align} \mathrm{R} \Gamma_{\mathrm{pro\acute{e}t} ,c}(X, \mathbf{Z}_\ell) \to \mathrm{R} \Gamma_{\mathrm{\acute{e}t} ,c}(X, \mathbf{Z}_\ell). \end{align} $$
Remark 2.5. If X is partially proper, we will show below (see Theorem 2.22) that the natural morphism in
${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
is a quasi-isomorphism. It follows that the map (2.4) induces a natural morphism in
${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
:
Proof. We first show that we have a quasi-isomorphism:
for any smooth rigid analytic variety Y. For that, choose a covering of Y by an increasing sequence of quasi-compact opens
$\{U_i\}_{i\in \mathbf {N}}$
. Since
it suffices to show the quasi-isomorphism (2.6) for a quasi-compact Y.
Assume thus that Y is quasi-compact. Then we have
using [Reference Scholze28, Cor. 3.17] . Since the functors
$\mathrm {R} \Gamma $
and
$\mathrm {R} \lim $
commute, we have
where the last quasi-isomorphism follows from [Reference Scholze28, Prop. 8.2]. Hence, we get the quasi-isomorphism (2.6), as wanted.
By the definitions of
$\mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} ,c}(X, \mathbf {Z}_{\ell })$
and
$\mathrm {R}\Gamma _{\mathrm {\acute {e}t} ,c, {\mathrm naive}}(X, \mathbf {Z}_{\ell })$
, this induces a quasi-isomorphism:
and composing with the natural morphism
$\mathrm {R}\Gamma _{\mathrm {\acute {e}t} ,c, {\mathrm naive}}(X, \mathbf {Z}_{\ell }) \to \mathrm {R}\Gamma _{\mathrm {\acute {e}t} ,c}(X, \mathbf {Z}_{\ell })$
, we obtain the morphism from the second claim of the lemma.
The above cohomologies satisfy all the properties from Section 2.1, that is, for
$\Lambda \in \{\mathbf {Z}/\ell ^n\mathbf {Z},\mathbf {Z}_\ell ,\mathbf {Q}_\ell \}$
, we have (here,
$*=\mathrm {\acute {e}t} , \mathrm {pro\acute {e}t} $
):
-
1. We have the distinguished triangles:
$$\begin{align*}\mathrm{R} \Gamma_{*,c}(X, \Lambda) \to \mathrm{R} \Gamma_{*}(X, \Lambda) \to \mathrm{R} \Gamma_{*}(\partial X, \Lambda). \end{align*}$$
-
2. If X is quasi-compact, we have quasi-isomorphisms:
$$\begin{align*}\mathrm{R} \Gamma_{*,c}(X, \Lambda) \xrightarrow{\sim} \mathrm{R} \Gamma_{*}(X, \Lambda). \end{align*}$$
In particular, if X is proper its cohomology with compact support coincides with the usual cohomology.
-
3. Let $j:U\hookrightarrow X$
be a relatively partially proper open subspace of X, we have a canonical map $$ \begin{align*}j_*: \quad \mathrm{R}\Gamma_{*,c}(U, \Lambda) \to \mathrm{R}\Gamma_{*,c}(X, \Lambda) .\end{align*} $$
Remark 2.7. As we have seen above, if X is quasi-compact, the cohomology of the boundary of X is trivial, that is,
$\mathrm {R} \Gamma _{\mathrm {\acute {e}t} }(\partial X, \Lambda ) =0$
. Hence, in this case, our definition is not the correct one. For torsion coefficients, the étale cohomology with compact support of Huber
$H^i_{\mathrm {\acute {e}t} ,c, \mathrm {Hu}}(X, \mathbf {Z}/\ell ^n\mathbf {Z})$
gives the right groups. For example, if
$\ell \neq p$
and
$X=\mathrm {Sp}(C\{T\})$
is the closed unit ball, we have (see [Reference Huber20, Example 0.4.6])
2.2.2. Comparison with the cohomology of Huber: Integral coefficients
Compactly supported étale cohomology was previously defined by Huber in [Reference Huber19], [Reference Huber20]. The purpose of this section is to prove the following comparison theorem.
Theorem 2.8. Let
$L=K,C$
and let
$\ell $
be a prime number. Assume that X is partially proper over L. Then there exist natural quasi-isomorphisms in
${\mathscr {D}}(\mathbf {Z}_{\ell ,\Box })$
Let us start with reviewing the definition of cohomology with compact support of Huber from [Reference Huber19, Chapter 5] (and extended to the
$\ell $
-adic case in [Reference Huber20]).
(i) Torsion coefficients. Let A be a ring and let
$f: X \to Y$
be a separated morphism of separated rigid analytic varieties.
Definition 2.9. For
$\mathscr {F}$
, a sheaf of
$\mathrm {mod}(X_{\mathrm {\acute {e}t} }-A)$
, we define
$\Gamma _c(X/Y, \mathscr {F})$
in the following way:
-
1. If X and Y are qcqs, we choose an integral model $\tilde {f}: \mathfrak {X} \to \mathfrak {Y}$
of f and set $$ \begin{align*} \Gamma_c(X/Y, \mathscr{F}) := \{ s \in \Gamma(X, \mathscr{F}) \; | \; \text{ there exists closed }\mathfrak{Z} \subset \mathfrak{X} \text{ such that } \mathfrak{Z} \to \mathfrak{Y} \text{ is proper }\\ \text{ and } s|_{{\mathrm sp}^{-1}(\mathfrak{X} \setminus \mathfrak{Z})}=0 \}, \end{align*} $$
where ${\mathrm sp} : X \to \mathfrak {X}$
is the specialization morphism. -
2. If Y is qcqs, we set
$$ \begin{align*} \Gamma_c(X/Y, \mathscr{F}) := \{ s \in \Gamma(X, \mathscr{F}) \; |& \; \text{there exists } \{U,V\}, \text{ an admissible open covering of } X, \\& \text{ such that } U \text{ is quasi-compact, } s|_U \in \Gamma_c(U/Y, \mathscr{F}|_U) \text{ and, } s_{V}=0 \}. \end{align*} $$
-
3. In the general case, we set
$$ \begin{align*} \Gamma_c(X/Y, \mathscr{F}) := \{ s \in \Gamma(X, \mathscr{F}) \; |& \; \text{for all } W \subset Y \text{ admissible open qcqs,} \\& s|_{f^{-1}(W)} \in \Gamma_c(f^{-1}(W)/W, \mathscr{F}|_{f^{-1}(W)}) \}. \end{align*} $$
If X is a rigid analytic variety over C, we write simply
$\Gamma _c(X, \mathscr {F})$
pour
$\Gamma _c(X/ \mathrm {Sp}(C), \mathscr {F})$
. Huber defined the functor
$f_{!} : \mathrm {mod}(X_{\mathrm {\acute {e}t} }-A) \to \mathrm {mod}(Y_{\mathrm {\acute {e}t} }-A)$
by setting
for an étale open U of Y (see [Reference Huber19, Paragraph 5.6.2]).
Remark 2.10. If
$X\to Y$
is a morphism of adic spaces, we write
$\Gamma _c(X/Y, \mathscr {F})$
for the set of global sections of
$\mathscr {F}$
whose support is proper over Y. If now
$X \to Y$
is a morphism of rigid analytic varieties as above and
$r(X) \to r(Y)$
is the morphism of associated adic spaces, we have an isomorphism (see [Reference Huber19, Lemma 5.6.4]):
where
$\rho $
is the natural morphism
$r(X)_{\mathrm {\acute {e}t} } \to X_{\mathrm {\acute {e}t} }$
.
(ii)
$\ell $
-adic coefficients. Denote by
$\mathrm {mod}(X_{\mathrm {\acute {e}t} }-\mathbf {Z}_{\ell }^{\bullet })$
the category of projective systems
$(\mathscr {F}_n)_n$
of
$\mathbf {Z}_{\ell }$
-modules on
$X_{\mathrm {\acute {e}t} }$
such that, for all
$n\in \mathbf {N}$
,
$\ell ^n\mathscr {F}_n=0$
. Consider
$X\to Y:= \mathrm {Spa}(L, {\mathscr O}_L)$
, a separated adic space locally of finite typeFootnote
5
and assume that X is taut. If X is partially proper, we define
$\mathrm {R} \Gamma _{\mathrm {\acute {e}t} , c, \mathrm {Hu}}(X,-)$
as the right derived functor of the functor
In the general case, there exists a factorization

where i is an open immersion and
$\overline {X} \to Y$
is partially proper. We then define
where
$i_! {\mathscr {G}}$
is the functor
$U \mapsto \Gamma _c(X \times _YU, {\mathscr {G}})$
.
For X, a separated rigid analytic variety over C, we define
$\mathrm {R} \Gamma _{\mathrm {\acute {e}t} , c, \mathrm {Hu}}(X, (\mathscr {F}_n)_n):= \mathrm {R} \Gamma _{\mathrm {\acute {e}t} , c, \mathrm {Hu}}(r(X),(\rho ^*\mathscr {F}_n)_n)$
. If X is partially proper,
$\mathrm {R} \Gamma _{\mathrm {\acute {e}t} ,c, \mathrm {Hu}}(X,-)$
is equal to the right derived functor of the functor
$(\mathscr {F}_n)_n \mapsto \Gamma _c(X_{\mathrm {\acute {e}t} }, \varprojlim _n \mathscr {F}_n)$
.
We will need the following well-known technical result.
Lemma 2.11. Let
$(\mathscr {F}_n)_n\in \mathrm {mod}(X_{\mathrm {\acute {e}t} }-\mathbf {Z}_{\ell }^{\bullet })$
. There exists a monomorphism
$(\mathscr {F}_n)_n \hookrightarrow (\mathscr {I}_n)_n$
from
$(\mathscr {F}_n)_n$
to
$(\mathscr {I}_n)_n$
, an object of
$\mathrm {mod}(X_{\mathrm {\acute {e}t} }-\mathbf {Z}_{\ell }^{\bullet })$
of the form
where the maps
$\mathscr {I}_n \to \mathscr {I}_{n-1}$
are given by the canonical projections and
$\mathscr {J}_s$
are injective sheaves of
$\mathbf {Z}/\ell ^s$
-modules on
$X_{\mathrm {\acute {e}t} }$
.
Moreover, for all n, the sheaf
$\mathscr {I}_n$
is an injective object of
$\mathrm {mod}(X_{\mathrm {\acute {e}t} }-\mathbf {Z}/\ell ^n)$
and the canonical map
$\mathscr {F}_n \to \mathscr {I}_n$
is a monomorphism.
Proof. We will recall here the proof from [Reference Jannsen21, Prop. 1.1]. For all s, we choose a monomorphism
$\mathscr {F}_s \to \mathscr {J}_s$
of
$\mathscr {F}_s$
into an injective object of the category of sheaves of
$\mathbf {Z}/\ell ^s$
-modules and we define the projective system
$(\mathscr {I}_n)_n$
as in the statement of the lemma. Since the
$\mathscr {J}_s$
’s are injective,
$(\mathscr {J}_s)_{s\in \mathbf {N}}$
is an injective object of the product category
and
$(\mathscr {F}_s)_s \to (\mathscr {J}_s)_s$
is a monomorphism in that category. The functor
admits left adjoint given by the forgetful functor
Since V is exact and faithful, the functor P preserves monomorphisms and injective objects. It follows that
$(\mathscr {I}_n)_n:=P((\mathscr {J}_s)_s)$
is an injective object and we have a monomorphism
$(\mathscr {F}_n)_n\to (\mathscr {I}_n)_n$
.
Conversely, for all
$m\in \mathbf {N}$
, the functor
also admits an exact faithful left adjoint:
It follows that
$V_n$
preserves monomorphisms and injectives. Hence, we have obtained that
$\mathscr {F}_n \to \mathscr {I}_n= V_n((\mathscr {I}_m)_m)$
is a monomorphism of
$\mathscr {F}_n$
into an injective sheaf
$\mathscr {I}_n$
, as wanted.
Remark 2.12. This lemma allows us to construct injective resolutions
$(\mathscr {F}_n)_n \to (\mathscr {I}_n)^{\bullet }_n$
such that the induced sequences
$\mathscr {F}_n \to \mathscr {I}_n^{\bullet }$
are also injective resolutions.
We can now prove the following proposition.
Proposition 2.13 (Huber [Reference Huber20, Cor. 5.3.6]).
There exists an isomorphism of exact functors from
$D^+(\mathrm {mod}(X_{{\text {\'et}}}- \mathbf {Z}_{\ell }^{\bullet }))$
to
$D^+(\mathrm {mod}(\mathbf {Z}_{\ell })):$
where
$\pi _*$
is the discretization functor
and
$\Gamma _{!}$
is the functor
Proof. By definition,
$\mathrm {R} \Gamma _{\mathrm {\acute {e}t} , c, \mathrm {Hu}}(X,-)$
is equal to the functor
$\mathrm {R} (\Gamma _c \circ \pi _*)$
. Take a resolution
$(\mathscr {F}_n)_n \to (\mathscr {I}_n)^{\bullet }_n$
given by Remark 2.12. The functor
$\pi _*$
is given by
$(\mathscr {F}_n)_n \mapsto \lim _n \mathscr {F}_n$
, hence, we have
This yields
But, by [Reference Huber19, (5.2.6)], every term of the complex
$\prod _{s \in \mathbf {N}} \mathscr {J}^{\bullet }_n$
is
$\Gamma _!$
-acyclic, hence, we have
We have obtained that
$\mathrm {R} (\Gamma _! \circ \pi _*)\simeq \mathrm {R} \Gamma _{!} \circ \mathrm {R} \pi _*$
, as wanted.
Later on we will need the following lemma.
Lemma 2.14. For
$(\mathscr {F}_n)_n$
in
$\mathrm {mod}(X_{\mathrm {\acute {e}t} }-\mathbf {Z}_{\ell }^{\bullet })$
, there exists a quasi-isomorphism
Proof. As in the proof of the previous proposition, take an injective resolution
$(\mathscr {F}_n)_n \to (\mathscr {I}_n)^{\bullet }_n$
given by Remark 2.12. We have
$\pi _*((\mathscr {I}_n)^{\bullet }_n)= \prod _{s \in \mathbf {N}} \mathscr {J}^{\bullet }_s$
. But each term of the complex
$\prod _{s \in \mathbf {N}} \mathscr {J}^{\bullet }_s$
is
$\Gamma $
-acyclic and
$\Gamma $
commutes with countable products, hence, we get
Remark 2.12 also gives us, for all n, an injective resolution
$\mathscr {F}_n \to \mathscr {I}^{\bullet }_n$
of
$\mathscr {F}_n$
. Hence,
which proves our lemma.
(iii) Comparison theorem. Let
$L=K,C$
. Assume in this section that X is partially proper over L. For a quasi-compact open Z and a sheaf of
$\mathbf {Z}_{\ell }$
-module
$\mathscr {F}$
on
$X_{\mathrm {\acute {e}t} }$
, define
and
$H^i_Z(X_{\mathrm {\acute {e}t} }, \mathscr {F}) := H^i \mathrm {R} \Gamma _Z(X_{\mathrm {\acute {e}t} }, \mathscr {F})$
the associated cohomology.
Lemma 2.15 (Huber [Reference Huber19, Proposition 5.6.5]).
For all
$\mathscr {F}$
in
$\mathrm {mod}(X_{{\text {\'et}}}-\mathbf {Z}_{\ell })$
, we have
In particular,
$\Gamma _c(X_{\mathrm {\acute {e}t} }, \mathscr {F})= \mathrm {colim} _{Z \in \Phi } \Gamma _Z(X_{\mathrm {\acute {e}t} }, \mathscr {F})$
.
Proof. If s is in
$\Gamma _c(X_{\mathrm {\acute {e}t} }, \mathscr {F}),$
then, by definition (see (2.9)), there exists an admissible open covering
$(Z, V)$
, with Z quasi-compact open, such that
$s|_V=0$
. Since
$V\supset X\setminus Z$
, we have
$s|_{X \setminus Z}=0$
as well.
Conversely, let s be such that
$s|_{X \setminus Z}=0$
, for Z admissible open and quasi-compact. Let
$X= \bigcup _{i \in I} X_i$
be an admissible covering of X with
$X_i$
open affinoid and such that, for all i, there exists
$\tilde {X}_i$
an open affinoid of X with
$X_i \Subset \tilde {X}_i$
. Since Z is quasi-compact, modulo reindexing, we may assume that
$Z \subset X_1 \cup X_2 \cup \dots \cup X_n$
, for a constant n. Set
$V:=X \setminus (X_1 \cup \dots \cup X_n)$
and
$\tilde {V}:= \tilde {X}_1 \cup \dots \cup \tilde {X}_n$
. Then
$\{V, \tilde {V} \}$
is an admissible open covering of X and
$s|_{V}=0$
.
Take a formal model
$\tilde {\mathfrak {V}}$
of
$\tilde {V}$
and the opens
$\mathfrak {X}_i$
and
$\tilde {\mathfrak {X}}_i$
of
$\tilde {\mathfrak {V}}$
with
$\mathfrak {X}_i \subset \tilde {\mathfrak {X}}_i$
and
$X_i= {\mathrm sp}^{-1}(\mathfrak {X}_i)$
,
$\tilde {X}_i= { \mathrm sp}^{-1}(\tilde {\mathfrak {X}}_i)$
(where
${\mathrm sp} : \tilde {V} \to \tilde {\mathfrak {V}}$
is the specialization map). If we write
$\bar {\mathfrak {X}}_i$
for the closure of
$\mathfrak {X}_i$
in
$\tilde {\mathfrak {X}}_i$
, then
$\bar {\mathfrak {X}}_i$
is proper over
${\mathscr O}_L$
(by [Reference Lütkebohmert25, Lemma 2.5]). Let now
$\mathfrak {Z}:= \bar {\mathfrak {X}}_1 \cup \dots \cup \bar {\mathfrak {X}}_n$
. Then
$\mathfrak {Z}$
is proper over
${\mathscr O}_L$
and
$\mathrm {sp}^{-1}(\tilde {\mathfrak {V}} \setminus \mathfrak {Z}) \subset (X \setminus Z)$
hence
$s|_{ \mathrm {sp}^{-1}(\mathfrak {X} \setminus \mathfrak {Z})}=0$
. We have proved that
$s \in \Gamma _c(X_{\mathrm {\acute {e}t} }, \mathscr {F})$
.
Denote by F the functor
Proposition 2.16 (van der Put [Reference van der Put30, Lemma 1.3]).
For all sheaves
$\mathscr {F}$
of
$\mathrm {mod}(X_{\mathrm{\acute{e}t}} - \mathbf {Z}_{\ell })$
, there exists a natural quasi-isomorphism
Proof. It suffices to check that, for all quasi-compact opens Z, we have a distinguished triangle:
where
$\mathrm {R} \Gamma _Z(X_{\mathrm {\acute {e}t} }, -)$
is the right derived functor of
$\mathscr {F} \mapsto \Gamma _Z(X_{\mathrm {\acute {e}t} }, \mathscr {F})$
.
To prove that, take the injective resolution
$\mathscr {F}\to \mathscr {I}^{\bullet }(\mathscr {F}) $
defined as follows. For
$n=0$
, we set
$\mathscr {I}^{-1}(\mathscr {F}) =\mathscr {F}$
and
$\mathscr {I}^0(\mathscr {F})(U):= \prod _{x \in U} \widetilde {\mathscr {F}}_x$
, where the product is taken over the geometric points x of X such that
$x \in U$
and
$\widetilde {\mathscr {F}}_x$
is the injective envelope of
$\mathscr {F}_x$
. We define then by induction
$\mathscr {I}^{n+1}(\mathscr {F}):=\mathscr {I}^0(\mathscr {I}^{n}(\mathscr {F})/\mathscr {I}^{n-1}(\mathscr {F}))$
. We have that
$\Gamma _{\mathrm {\acute {e}t} }(X, \mathscr {I}^n({\mathscr {F}})) \to \Gamma _{\mathrm {\acute {e}t} }(X \setminus Z, \mathscr {I}^n({\mathscr {F}}))$
is surjective, for all
$n \ge 0$
. It follows that the sequence of complexes
is exact, as wanted.
Corollary 2.17. For all sheaves
$\mathscr {F}\in \mathrm {mod}(X_{\mathrm{\acute{e}t}} - \mathbf {Z}_{\ell })$
, we have a natural quasi-isomorphism
Proof.
$\mathrm {R} \Gamma _{!}(X,-)$
is the right derived functor of the functor
$\mathscr {F} \mapsto \Gamma _c(X_{\mathrm {\acute {e}t} }, \mathscr {F})$
, and hence, it is equal to
$\mathrm {R} F$
by Lemma 2.15. The result follows now directly from Proposition 2.16.
Proof. Proof. (of Theorem 2.8).
We want to show that
For that, consider the following quasi-isomorphisms:
The first and second quasi-isomorphisms follow from Proposition 2.13 and Corollary 2.17, respectively. The third one follows from Lemma 2.14. The equality in the fourth row is obtained from the definition of
$\ell $
-adic étale cohomology.
Example 2.18. (Cohomology with compact support of the affine line
${\mathbb A}_C^1$
).
Lemma 2.19. We have quasi-isomorphisms of solid
$\mathbf {Z}_{\ell }$
and
$ \mathbf {Z}_p$
-modules, respectively
$:$
Proof. Recall that for all primes
$\ell $
(including
$\ell =p$
), we have
For
$j \in \mathbf {N}$
, consider the closed discs
and the associated distinguished triangle (1):
Write
$C_j:=\{z \in {\mathbb A}^1_C, |z| \ge p^j\}$
, then
Consider
$E_j:=\{z \in \mathbb {P}^1, |z| \ge p^j\}$
so that
$C_j={\mathbb A}^1_C \cap E_j$
. The Kummer sequence gives
Using the Mayer–Vietoris sequence for
$\mathbb {P}^1_C=E_j \cup {\mathbb A}^1_C$
, we get
If
$\ell \neq p$
, then
$C\{(p^jz)^{-1}\}^{*}$
is
$\ell $
-divisible, and we get
Using (2.21) and the isomorphism, via the logarithm (see [Reference Colmez, Dospinescu, Hauseux and Nizioł9, Example A.2]),
$ \mathrm {colim} _jC\{(p^jz)^{-1}\}^{*\wedge }\simeq ({\mathscr O}_{{\mathbb P}^1,\infty }/C), $
this yields (2.20), as wanted.
In particular, the above result recovers the groups
$H^2_{\mathrm {\acute {e}t} ,c, {\mathrm {Hu}}}({\mathbb A}^1_C, \mathbf {Z}_{\ell }(1))$
and
$H^2_{\mathrm {\acute {e}t} ,c, {\mathrm {Hu}}}({\mathbb A}^1_C, \mathbf {Z}_p(1))$
computed in [Reference Colmez, Dospinescu, Hauseux and Nizioł9, Example (A.2)] in accordance with Theorem 2.8.
For the rational cohomology, we will see later (see Example 7.3) using syntomic techniques that we have
Using the long exact sequence defining
$H^1_c({\mathbb A}^1_C, {\mathscr O})$
and the vanishing of the coherent cohomology of
${\mathbb A}^1_C$
, we obtain
$H^1_c({\mathbb A}^1_C, {\mathscr O}) \simeq {\mathscr O}(\partial {\mathbb A}^1_C)/ {\mathscr O}({\mathbb A}^1_C)$
and
In particular, we see that
$H^i_{\mathrm {pro\acute {e}t} ,c}({\mathbb A}^1_C, \mathbf {Q}_p(1)) \simeq H^i_{\mathrm {\acute {e}t} ,c, {\mathrm {Hu}}}({\mathbb A}^1_C, \mathbf {Z}_p(1)) \otimes ^{\Box }_{\mathbf {Z}_p} \mathbf {Q}_p$
for all i. As we will show in Theorem 2.22, this is a general phenomena.
2.2.3. Comparison with the cohomology of Huber: Rational coefficients
The goal of this section is to prove the following theorem.
Theorem 2.22. Let X be a partially proper rigid analytic variety over
$L=K,C$
. The quasi-isomorphism
$\mathrm {R}\Gamma _{\mathrm {\acute {e}t} ,c, {\mathrm {Hu}}}(X, \mathbf {Z}_{\ell }) \xrightarrow {\sim } \mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} ,c}(X, \mathbf {Z}_{\ell })$
from Theorem 2.8 induces a quasi-isomorphism in
${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
where we set
.
We precede the proof with a handful of remarks. Thanks to Theorem 2.8, we have a quasi-isomorphism in
${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
Therefore, Theorem 2.22 is equivalent to the following result, which has nothing to do with Huber’s compactly supported cohomology anymore.
Lemma 2.23. Let X be a partially proper rigid analytic variety over
$L=K,C$
. Then, the natural morphism in
${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
is a quasi-isomorphism.
Note that the same result is not true without compact support as the following basic example shows.
Example 2.24. Let
$X={\mathbb A}^{1}_C$
. Then the map
is not a quasi-isomorphism. Indeed, by [Reference Colmez, Dospinescu and Nizioł8, Theorem 1.8], the
$H^1$
of the target equals
while the source
$H^1_{\mathrm {pro\acute {e}t} }(X, \mathbf {Z}_p)$
vanishes (e.g., by comparison with the cohomology of the scheme
$H^1_{\mathrm{\acute{e}t}}({\mathbb A}^1_C, \mathbf {Z}_p)=0$
).
In order to measure the failure of (2.25) being a quasi-isomorphism, let us introduce the following notation for its mapping fiber:
Naturally, a morphism
$Y\to X$
induces a map
$P(X)\to P(Y)$
.
Below, we see rigid spaces as adic spaces, and we use the language of adic geometry.
Lemma 2.26. Let X be a rigid space and let
$U\subseteq X$
be a retrocompact open. Then the closure
$\overline {U}$
of U in X consists of all specializations of points of U. Moreover, U is equal to the interior of
$\overline {U}$
.
Proof. This follows from a result in general topology [Reference Fujiwara and Kato17, Chapter 0, Corollary 2.2.27, and Proposition 2.4.4] combined with the fact that the underlying topological spaces of rigid spaces (in Fujiwara–Kato’s sense) of type
$V_{\mathbf {R}}$
are reflexive valuative spaces [Reference Fujiwara and Kato17, Chapter II, Theorem 8.2.19]. Since the result is less difficult than having to move between different formalisms, we give a proof below.
Let
$U'$
be the interior of
$\overline {U}$
in X. Trivially,
$U\subseteq U'$
and we need to show the reverse inclusion. The underlying topological space of X is a locally spectral space, so by [Reference Fujiwara and Kato17, Chapter 0, Corollary 2.2.27], the closure
$\overline {U}$
consists of all specializations of points of U inside X. Therefore, U and
$U'$
have the same closed points, in particular the same classical points.
Let
$V\subseteq U'$
be an affinoid open. As
$U\hookrightarrow X$
is quasi-compact, the map
$U\cap V\hookrightarrow V$
is an open immersion of qcqs rigid spaces which is surjective on classical points. It follows that
$U\cap V = V$
, and since V was arbitrary, that
$U \subseteq U'$
.
Lemma 2.27. Let X be a qs rigid space, let
$U,V\subseteq X$
be quasi-compact opens such that
$U\subset V$
. Then
$U\Subset V$
if and only if there exists a partially proper
$U'$
with
$U\subseteq U'\subseteq V$
. Moreover, one can pick
$U'$
so that
$(X\setminus U')^\circ $
is a retrocompact open and
$(X\setminus U')^\circ \cup V = X$
.
Proof. Let
$\mathfrak {U}\subseteq \mathfrak {V}$
be an open immersion of admissible formal schemes over
$\mathscr {O}_L$
which is a formal model of
$U\subseteq V$
, which exists because U and V are qcqs. The assumption that
$U\Subset V$
translates into the statement that
$Z:=\overline {\mathfrak {U}_0}$
(the closure of the special fiber of
$\mathfrak {U}$
inside the special fiber of
$\mathfrak {V}$
) is proper over k. Let
$U'\subseteq V$
be the Berthelot tube of Z, that is, the interior of its preimage
$\mathrm {sp}^{-1}(Z)$
under the specialization map
$\mathrm {sp}\colon V\to \mathfrak {V}_0$
. Then
$U'$
is a partially proper open of V containing U by construction.
Lemma 2.26 above implies that the quasi-compact open
$W = \mathrm {sp}^{-1}(\mathfrak {V}_0\setminus Z)$
is the interior of its closure, so that
$\mathrm {sp}^{-1}(Z)$
is the closure of its interior. This in turn implies that the interior
$(V\setminus U')^\circ $
of
$V\setminus U'$
equals W and hence is quasi-compact.
Finally, we claim that
Suppose we know this to hold, then
$X\setminus V\subseteq (X\setminus U')^\circ $
implies that
$X = V\cup (X\setminus U')^\circ $
. Moreover, we can check that
$(X\setminus U')^\circ $
is retrocompact on the open cover
$X = V \cup (X\setminus U')^\circ $
, and we are done.
It remains to show that if
$x\in X\setminus V$
belongs to the closure of V, then it lies in the closure of the quasi-compact open
$W = (V\setminus U')^\circ $
. As taking the closure of a qc open amounts to adding specializations (Lemma 2.26 again), there exists a point
$y\in V$
specializing to x, and x belongs to the closure of W if and only if y does. But if y is not in the closure of W, it belongs to the interior of
$X\setminus W$
, which equals
$U'$
. Since
$U'$
is partially proper, it is closed under specialization in X (by the valuative criterion), and hence
$x\in U'$
, a contradiction.
Corollary 2.28. Let X be a partially proper rigid space. Then X can be written as the filtered colimit of opens
$U\subseteq X$
with the following properties:
-
1. U is partially proper;
-
2. the closure of U in X is quasi-compact;
-
3. $(X\setminus U)^\circ $
is retrocompact in X.
Moreover, such a family is cofinal with the family of quasi-compact opens of X.
Proof. Since X is partially proper, it can be written as the filtered colimit of a family of quasi-compact opens
$\{U_i\}_{i\in I}$
such that, for every
$i\in I,$
there exists a
$j\in I$
with
$j>i$
such that
$U_i\Subset U_j$
. Pick such a j for every i. Applying Lemma 2.27 to
$U_i\Subset U_j\subseteq X$
, we obtain an open subset
$U^{\prime }_i$
with
$U_i\subset U^{\prime }_i\subset U_j$
which satisfies (1)–(3). It is easy to see that the resulting family of subsets (possibly no longer indexed by I) is cofiltering, and trivially covers X.
Remark 2.29. The assertion of Corollary 2.28 is obvious in the Stein case. Embed
$X\subseteq \mathbf {A}^{r}_L$
as a closed analytic subspace, let
$U_n = X\cap D(0,|p|^{-n})^r$
be the intersection with a large closed polydisc, an affinoid open of X, and let
$U^{\prime }_n = X\cap D^\circ (0, |p|^{-n})^r$
be the intersection with the corresponding open polydisc, a pp open of X containing
$U_{n-1}$
. Then
This is a finite union of affinoid rational domains hence is quasi-compact. Therefore,
$(X\setminus U^{\prime }_n)^\circ $
is retrocompact in X.
Lemma 2.30. Let X be a rigid analytic variety over
$L=K,C$
.
-
1. If X is quasi-compact, then $P(X) = 0$
(i.e., (2.25) is a quasi-isomorphism). -
2. If X is partially proper, then $P(X)\to P(\partial X)$
is an isomorphism.
Proof. Claim (1) is clear. For claim (2), write X as the filtering colimit of opens
$U_i\subseteq X$
(
$i\in I$
) as in Corollary 2.28. Since the family is cofinal with the family of quasi-compact opens of X, we have
It is therefore enough to show that the map
$P(X)\to P((X\setminus U)^\circ )$
is an isomorphism for every U in the family. To this end, let
$V\subseteq X$
be a quasi-compact open containing U. Thus, X can be covered by the quasi-compact open V and the non-quasi-compact open
$(X\setminus U)^\circ $
whose intersection W is quasi-compact by retrocompactness of
$(X\setminus U)^\circ $
. We have a morphism of distinguished triangles

By (1), we have
$P(V) = 0 = P(W)$
, and it follows that
$P(X)\to P((X\setminus U)^\circ )$
is a quasi-isomorphism.
Proof of Lemma 2.23 (and therefore also of Theorem 2.22).
For every quasi-compact open
$U\subset X$
, let
$U'\subset U$
denote its interior, which is a partially proper open. Since X is partially proper, the subsets
$U'$
(as U varies over quasi-compact opens U) are cofinal with the subsets U (every U is contained in
$V'$
for some V), so that we have
and, similarly,
By Lemma 2.30, the map
$P(X)\to P(\partial X)$
is a quasi-isomorphism. Therefore, the square

is Cartesian. Flipping the square, we deduce that
$\mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} ,c}(X, \mathbf {Z}_{\ell })_{\mathbf {Q}_{\ell }} \to \mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} ,c}(X, \mathbf {Q}_{\ell })$
is a quasi-isomorphism as well, as wanted.
2.2.4. Properties
We will now list the following properties of Huber’s étale cohomology with compact support (hence, in the case, the spaces are smooth and partially proper, by Theorems 2.8 and 2.22, of the pro-étale cohomology with compact support). All the spaces are adic.
-
1. If X is proper, then we have a natural quasi-isomorphism in ${\mathscr {D}}(\mathbf {Z}_{\ell ,\Box })$
: $$ \begin{align*}\mathrm{R}\Gamma_{\mathrm{\acute{e}t} , \mathrm{c,Hu}}(X,\mathbf{Z}_\ell)\simeq \mathrm{R}\Gamma_{\mathrm{\acute{e}t} }(X,\mathbf{Z}_\ell). \end{align*} $$
-
2. If $j:U\hookrightarrow X$
is an open embedding, then we have the pushforward map in
${\mathscr {D}}(\mathbf {Z}_{\ell ,\Box })$
: $$ \begin{align*}j_*: \mathrm{R}\Gamma_{\mathrm{\acute{e}t} , \mathrm{ c,Hu}}(U,\mathbf{Z}_\ell) \to \mathrm{R}\Gamma_{\mathrm{\acute{e}t} , \mathrm{c,Hu}}(X,\mathbf{Z}_\ell).\end{align*} $$
-
3. If X is quasi-compact, there is an exact sequence [Reference Huber20, Corollary 2.4] of solid $\mathbf {Z}_{\ell }$
-modules $$ \begin{align*}0\to \mathrm{R}^1\varprojlim_nH^{i-1}_{\mathrm{\acute{e}t} ,c}(X,\mathbf{Z}/\ell^n)\to H^i_{\mathrm{\acute{e}t} ,\mathrm{c,Hu}}(X,\mathbf{Z}_\ell)\to \varprojlim_nH^i_{\mathrm{\acute{e}t} ,c}(X,\mathbf{Z}/\ell^n)\to 0. \end{align*} $$
-
4. Let U be a taut open subspace of X, let $Z=X\setminus U$
, and let
$i: Z\hookrightarrow X$
be the inclusion. Assume that
$X,U$
are partially proper. Then we have a distinguished triangle in
${\mathscr {D}}(\mathbf {Z}_{\ell ,\Box })$
$$ \begin{align*} \mathrm{R}\Gamma_{\mathrm{\acute{e}t} ,\mathrm{c,Hu}}(U,\mathbf{Z}_\ell|_{U}) \to \mathrm{R}\Gamma_{\mathrm{\acute{e}t} ,\mathrm{ c,Hu}}(X, \mathbf{Z}_\ell)\to \mathrm{R}\Gamma_{\mathrm{\acute{e}t} ,c}(Z, i^*\mathrm{R}\pi_*\mathbf{Z}_\ell). \end{align*} $$
-
5. Let ${\mathbb U} $
be an open covering of X such that every
$U \in {\mathbb U} $
is taut and, for every
$U, V\in {\mathbb U}$
, there exists a
$W \in {\mathbb U}$
such that
$U \cup V\subset W$
. Then, the map of solid
$\mathbf {Z}_{\ell }$
-modules $$ \begin{align*}\varinjlim_{U\in {\mathbb U}} H^i_{\mathrm{\acute{e}t} ,\mathrm{c,Hu}} (U,\mathbf{Z}_\ell|_{U})\to H^i_{\mathrm{\acute{e}t} , \mathrm{c,Hu}} (X,\mathbf{Z}_\ell),\quad i\geq 0,\end{align*} $$
is an isomorphism [Reference Huber20, Proposition 2.1].
-
6. Let $\{U\}_{i\in I}$
be an admissible open covering of X by taut open varieties. There is a spectral sequence [Reference Huber20, Proposition 2.5] (2.31) $$ \begin{align}E_1^{a,b}= \bigoplus_{J\subset I, |J|=-a+1}H^b_{\mathrm{\acute{e}t} , \mathrm{c, Hu}}(U_J, \mathbf{Q}_\ell(r)|_{U_J}) \Rightarrow H^{a+b}_{\mathrm{\acute{e}t} ,\mathrm{c, Hu}}(X, \mathbf{Q}_\ell(r)). \end{align} $$
-
7. Let X be adic and partially proper and let G be a locally profinite group acting continuously on X. Then $H^i_{\mathrm {\acute {e}t} ,c}(X,\mathbf {Z}/\ell ^n)$
,
$i\geq 0$
, is a smooth G-module [Reference Berkovich2, Corollary 7.8].
2.3. Overconvergent setting
We define and study compactly supported
$\ell $
-adic pro-étale cohomology of smooth dagger varieties over K or C. As usual, we first give a local definition via presentations of dagger affinoids and then globalize it. We show that this definition coincides with the rigid analytic one for partially proper varieties.
2.3.1. Definition
We refer the reader to [Reference Colmez and Nizioł14, Chapter 3] for the definition of pro-étale cohomology of dagger varieties. Here, we define the overconvergent pro-étale cohomology with compact support by the following process: locally, if X is a dagger affinoid over
$L=K,C$
with a presentation
$\mathrm {pres}(X)=\{X_h\}_{h\in \mathbf {N}}$
of the dagger structureFootnote
6
and rigid completion
$\widehat {X}$
, we define in
${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
where
Putting it together, we get
This form makes it clear that
$\mathrm {R}\Gamma ^{\natural }_{\mathrm {pro\acute {e}t} ,c}(X,\mathbf {Q}_{\ell }(r))$
is covariant for open embeddings. Indeed, let
$U\to X$
be an open embedding of smooth dagger affinoids. Choose compatible presentations
$\{U_h\}$
and
$\{X_h\}$
(i.e., so that the maps
$U_h\to X_h$
are also open embeddings). We define the pushforward map
$\mathrm {R}\Gamma ^{\natural }_{\mathrm {pro\acute {e}t} ,c}(U,\mathbf {Q}_{\ell }(r))\to \mathrm {R}\Gamma ^{\natural }_{\mathrm {pro\acute {e}t} ,c}(X,\mathbf {Q}_{\ell }(r))$
via the composition
Here, the first arrow is a quasi-isomorphism by the excision (2.1).
For a general smooth dagger variety X over L, we define the cosheaf
${\mathscr {A}}_{\mathrm {pro\acute {e}t} ,c}(r)$
on X as the cosheafFootnote
7
associated with the precosheaf defined by
$U\mapsto \mathrm {R}\Gamma ^{\natural }_{\mathrm {pro\acute {e}t} ,c}(U,\mathbf {Q}_{\ell }(r)), U\in \mathrm {SmAff}^{\dagger }_{L}$
,
$U\to X$
an open embedding. We set
If
$ L =K$
, it is a dg
$\mathbf {Q}_{\ell }$
-algebra equipped with a continuous action of
${\mathscr {G}}_K$
.
Lemma 2.34. Let
$L=K,C$
. Let X be in
$\mathrm {Sm}_L^{\dagger }$
.
-
1. (Local–global compatibility) If X is a dagger affinoid, then the natural map in ${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
$$ \begin{align*}\mathrm{R}\Gamma_{\mathrm{pro\acute{e}t} ,c}(X,\mathbf{Q}_\ell(r))\to \mathrm{R}\Gamma^{\natural}_{\mathrm{pro\acute{e}t} ,c}(X,\mathbf{Q}_\ell(r))\end{align*} $$
is a quasi-isomorphism.
-
2. (Passing to completion) If X is partially proper, then there is natural quasi-isomorphism in ${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
$$ \begin{align*}\mathrm{R}\Gamma_{\mathrm{pro\acute{e}t} ,c}({X},\mathbf{Q}_\ell(r))\stackrel{\sim}{\to} \mathrm{R}\Gamma_{\mathrm{pro\acute{e}t} ,c}(\widehat{X},\mathbf{Q}_\ell(r)). \end{align*} $$
Proof. For the first claim, it suffices to show that, for any open covering
$X=X_1\cup X_2$
by dagger affinoids, we have the Mayer–Vietoris distinguished triangle
Choosing a presentation
$\{ X_h \}$
of X, an
$h\in \mathbf {N}$
, and using excision, we can write this triangle as
which is known to be distinguished.
Let us now prove claim (2). If X is Stein, take
$\{ U_n \}$
an increasing covering of X by admissible dagger affinoids. We have a commutative diagram:

where the first row is the distinguished triangle (1) and the second one—the distinguished triangle (2.39). (We note that there is no circular reasoning here: the proof of Proposition 2.37 uses only the first claim of this lemma.) The second and third vertical arrows are quasi-isomorphisms by the usual comparison results between overconvergent cohomologies and their rigid analytic analogs (see [Reference Colmez and Nizioł14, Proposition 3.17]). We obtain that the first vertical map (defined by the diagram) is a quasi-isomorphism as well.
Since a general partially proper variety X is locally Stein, we can conclude by analytic codescent.
Remark 2.35 (Comparison with the definition of Grosse-Klönne).
Compactly supported de Rham cohomology of dagger varieties was defined by Grosse-Klönne in [Reference Grosse-Klönne18] and we can consider its pro-étale version. For a smooth dagger affinoid X over
$L=K,C$
, set in
${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
(see [Reference Grosse-Klönne18, Section 4.3])
This is independent of h because of the excision (2.1).
Proposition 2.36. Let X be a smooth dagger affinoid. There is a quasi-isomorphism in
${\mathscr D}(\mathbf {Q}_{\ell ,\Box })$
:
Proof. This follows from the excision (2.1). Consider the following maps of distinguished triangles in
${\mathscr D}(\mathbf {Q}_{\ell ,\Box })$
:

The existence of the first and second distinguished triangles follows from the definition of
$\mathrm {R}\Gamma ^{\mathrm { GK}}_{\mathrm {pro\acute {e}t} ,c}(X,\mathbf {Q}_{\ell }(r))$
; of the last one from the definition of
$\mathrm {R}\Gamma ^{\natural }_{\mathrm {pro\acute {e}t} ,c}(X,\mathbf {Q}_{\ell }(r))$
. The left vertical map is a quasi-isomorphisms by the excision (2.1). Also the dotted arrow exists and clearly is a quasi-isomorphism. This concludes the proof.
Proposition 2.37. Let X be a smooth dagger Stein variety over
$L=K,C$
and let
$\{U_n\}_{n}$
be an admissible strict covering of X with dagger affinoids
$U_n \Subset U_{n+1}$
. Then there are natural quasi-isomorphisms in
${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
:
Remark 2.38. In particular, if we define the cohomology of the boundary of X as
we have a distinguished triangle:
as in the rigid analytic set-up.
Proof. Let X and
$\{U_n\}$
be as in the statement of the proposition. For each n, let
$\{U_{n,h} \}_h$
be a presentation of
$U_n$
. Then,
where the first quasi-isomorphism comes from the fact that
${\mathscr {A}}_{\mathrm {pro\acute {e}t} ,c}$
is a cosheaf, the second one is the local–global compatibility from Lemma 2.34, and the third one is the one from Proposition 2.36. For
$h \in \mathbf {N}$
, from the excision (2.1), we have
We conclude the proof using the quasi-isomorphisms
$\mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} }(\widehat {X},\mathbf {Q}_{\ell }(r))\xleftarrow {\sim }\mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} }(X,\mathbf {Q}_{\ell }(r))$
and
$\mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} }(\widehat {X}\setminus \widehat {U}_n,\mathbf {Q}_{\ell }(r))\xleftarrow {\sim }\mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} }(X \setminus U_n,\mathbf {Q}_{\ell }(r))$
.
2.3.2. Mayer–Vietoris sequence
By definition, our compactly supported pro-étale cohomology satisfies a Mayer–Vietoris distinguished triangle.
Proposition 2.40 (Mayer–Vietoris sequence for dagger varieties.).
Let X be a dagger variety over
$L=K,C$
and let
$X=U \cup V$
be an admissible open covering. Let
$r\geq 0$
. We have a distinguished triangle in
${\mathscr {D}}(\mathbf {Q}_{\ell ,\Box })$
:
Proof. The proposition follows from formula (2.33) and the cosheaf condition for
${\mathscr {A}}_{\mathrm {pro\acute {e}t} ,c}(r)$
.
3. Rigid analytic de Rham and Hyodo–Kato cohomologies with compact support
In this section, we define compactly supported de Rham,
${\mathbf B}_{\mathrm {dR}}^+$
-, and Hyodo–Kato cohomologies for smooth rigid analytic varieties over K or C. Our construction is inspired by the one of Chiarellotto in [Reference Chiarellotto6] (see also [Reference Beyer4], [Reference van der Put30]). The usual
${\mathbf B}_{\mathrm {dR}}^+$
- and Hyodo–Kato cohomologies we use here are the ones defined by Colmez and Nizioł in [Reference Colmez and Nizioł14], [Reference Colmez and Nizioł15].
We prove various properties and comparison theorems satisfied by the above cohomologies with compact support. Most of these results are the compactly supported analogs of the ones we have in the usual case (see [Reference Colmez and Nizioł14], [Reference Colmez and Nizioł15]).
3.1. De Rham cohomology with compact support
We begin by reviewing the definition of compactly supported de Rham cohomology of rigid analytic varieties introduced by Chiarellotto [Reference Chiarellotto6].
3.1.1. Definition of de Rham cohomology with compact support
Let
$L= K, C$
and let X be a smooth rigid analytic variety over L. Recall that the de Rham cohomology of
$X \in \mathrm {Sm}_L$
is defined as
where
$\Omega _X^{\bullet }$
is the complex of sheaves of differential forms and
$ {\mathscr {F}}{\mathscr D}(L_{\Box })$
is filtered
$\infty $
-category of
$ {\mathscr D}(L_{\Box })$
. As in Section 2.1, we set in
$ {\mathscr {F}}{\mathscr D}(L_{\Box })$
and write
$H^i_{\mathrm {dR} ,c}(X):=H^i\mathrm {R}\Gamma _{\mathrm {dR} ,c}(X)$
for the associated cohomology groups. We have
where the compactly supported coherent cohomology is defined by an analog of formula (3.1). We have equipped
$\mathrm {R}\Gamma _{\mathrm {dR} ,c}(X)$
with the Hodge filtration
Hence,
$\mathrm {R}\Gamma _{\mathrm {dR} ,c}(X)$
is a (solid) filtered dg L-algebra. We refer the reader to Section 2.1 for its basic properties.
3.1.2. Definition of
$\mathbf{B}^+_{\mathrm {dR} }$
-cohomology with compact support
The construction is analogous to the one above, using the definition of the rigid analytic
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology from [Reference Colmez and Nizioł15, §3.3].
(i) Rigid analytic
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology. Let us first recall how the usual
${\mathbf B}_{\mathrm {dR} }^+$
-cohomology is defined. Denote by
${\mathscr {M}}_C^{\mathrm {ss}}$
the category of semistable formal models and let
${\mathscr {X}} \in {\mathscr {M}}_C^{\mathrm {ss}}$
. By regarding the crystalline structure sheaf
${\mathscr {O}}_{\mathrm {cr} }$
and the divided power sheaves
${\mathscr {J}}^{[r]}$
,
$r \ge 0$
, as sheaves with values in condensed abelian groups, we can define the absolute crystalline cohomology
$\mathrm {R}\Gamma _{\mathrm {cr} }({\mathscr {X}})_{\mathbf {Q}_p}$
,
$\mathrm {R}\Gamma _{\mathrm {cr} }({\mathscr {X}}, {\mathscr {J}}^{[r]})_{\mathbf {Q}_p}$
in
${\mathscr D}(\mathbf {Q}_{p,\Box })$
. By completing with respect to its Hodge filtration and then taking the
$\eta $
-sheafification, we define sheaves
$F^r{\mathscr {A}}_{\mathrm {cr} }^{\underset {\widehat {\phantom {\ \ }}}{\phantom {\_}}}$
,
$r\ge 0$
on
$\mathrm {Sm}_{C, \mathrm {\acute {e}t} }$
with values in
${\mathscr D}({\mathbf B}_{\mathrm {dR} ,\Box }^+)$
. The
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology is then given by
It is a (solid) dg filtered
${\mathbf B}^+_{\mathrm {dR} }$
-algebra equipped with a continuous action of
${\mathscr {G}}_K$
if X is defined over K.
We have a canonical map in
${\mathscr {D}}(C_{\Box })$
(ii) Compactly supported
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology. Let
$X\in \mathrm {Sm}_C$
. Proceeding as in Section 2.1, we obtain compactly supported rigid analytic
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology in
$ {\mathscr D}({\mathbf B}_{\mathrm {dR} ,\Box }^+) $
starting with the rigid analytic
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology from the previous paragraph. It is a solid dg filtered
${\mathbf B}^+_{\mathrm {dR} }$
-algebra equipped with a continuous action of
${\mathscr {G}}_K$
if X is defined over K. It satisfies the properties listed in Section 2.1. We have a canonical map in
${\mathscr {D}}(C_{\Box })$
3.1.3. Comparison results
In this section, we give the analogs for compactly supported
${\mathbf B}_{\mathrm {dR} }^+$
-cohomology of the comparison results that we have in the classical case. We first recall the results from [Reference Colmez and Nizioł15, §3.3.2] formulating them in the solid world.
(i) Product formula. Let X be a smooth rigid analytic variety over K. We define filtrations on
and
by the formulas

Remark 3.2. For
$r \ge 0$
, we clearly have a distinguished triangle in
${\mathscr {D}}({{\mathbf B}^+_{\mathrm {dR} ,\Box }})$
:
Moreover, since
$ \mathrm {colim} _Z(-)$
commutes with
, we have a canonical quasi-isomorphism
Recall that, in the classical case, we have the following lemma.
Lemma 3.3 [Reference Colmez and Nizioł15, Lemma 3.17].
Let X be a smooth rigid analytic variety over K. Then, there is a filtered quasi-isomorphism in
${\mathscr D}({\mathbf B}_{\mathrm {dR} ,\Box }^{+})$
:
Proof. We can work étale locally. Consider the maps:

for
${\mathscr {X}}$
the base change to
${\mathscr {O}}_C$
of a semistable model
${\mathscr {X}}_{{\mathscr {O}}_L}$
over a finite extension L of K, and where we have defined
The first arrow in (3.4) is a quasi-isomorphism (use the fact that the ring
${\mathbf B}_{\mathrm {dR} }^+$
is the Hodge completed crystalline cohomology of the base ring
${\mathscr {O}}_{\overline {K}}$
). For the second map, we know that, by the Künneth formula, we have quasi-isomorphisms:
By taking the derived inverse limit over
$n\ge 1$
, we get a quasi-isomorphisms:
We then use [Reference Bosco5, Lemma A.9] to identify the left-hand side with the solid tensor product:
Inverting p, we obtain that the second map in (3.4) is a quasi-isomorphism. The third arrow in (3.4) is given by the base change from
${\mathscr {O}}_F^{\times }$
to
${\mathscr {O}}_L^{\times }$
and it is a quasi-isomorphism by [Reference Nekovář and Nizioł26, Corollary 2.4]. By taking the derived limit
$\mathrm {R}\lim _r \iota _{\mathrm {BK},r}$
, we get a quasi-isomorphism:
To conclude, it suffices to show that we have a quasi-isomorphism:
But this can be done as in [Reference Colmez and Nizioł15, Lemma 3.17], by writing the explicit definition of the filtration and arguing degreewise.
Applying the previous lemma to the varieties X and
$X \setminus Z$
, for
$Z\in \Phi _X$
, and using that the tensor product commutes with colimits, we obtain a filtered quasi-isomorphism in
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
for the compactly supported cohomologies:
Note that the compatibility with the filtrations follows from Remark 3.2.
(ii) Projection from
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology to de Rham cohomology. We can now compare the
${\mathbf B}^+_{\mathrm {dR} }$
- and de Rham cohomologies.
Recall that we have the following proposition.
Proposition 3.6 [Reference Colmez and Nizioł14, Proposition 3.11].
Let X be a smooth rigid analytic variety over C. Then,
-
1. We have a natural quasi-isomorphism in ${\mathscr D}(C_{\Box })$
: (3.7)
-
2. More generally, for $r\geq 0$
, we have a natural distinguished triangle in
${\mathscr D}({{\mathbf B}_{\mathrm {dR} ,\Box }^+}) $
: (3.8)
-
3. For $r\geq 0$
, we have a natural distinguished triangle in
${\mathscr D}({{\mathbf B}_{\mathrm {dR} ,\Box }^+}) $
: (3.9) $$ \begin{align} F^{r+1}\mathrm{R}\Gamma_{\mathrm{dR} }(X/{\mathbf B}^+_{\mathrm{dR} })\to F^r\mathrm{R}\Gamma_{\mathrm{dR} }(X/{\mathbf B}^+_{\mathrm{dR} })\stackrel{\beta_X}{\to} \bigoplus_{i\leq r}\mathrm{R}\Gamma(X,\Omega^i_X)(r-i)[-i]. \end{align} $$
Proof. The proof from [Reference Colmez and Nizioł14, Proposition 3.11] still works in the solid setting: working étale locally, we use the
$\iota _{\mathrm {BK}}$
from Lemma 3.3 to reduce to a similar statement for the de Rham cohomology instead of the crystalline one.
We deduce from the previous proposition its analog in the compactly supported case.
Proposition 3.10. Let X be a smooth rigid analytic variety over C. Then,
-
1. We have a natural quasi-isomorphism in ${\mathscr D}(C_{\Box })$
: 
-
2. More generally, for $r\geq 0$
, we have a natural distinguished triangle in
${\mathscr D}({{\mathbf B}_{\mathrm {dR} ,\Box }^+}) $
: (3.11)
-
3. For $r\geq 0$
, we have a natural distinguished triangle in
$ {\mathscr D}({{\mathbf B}_{\mathrm {dR} ,\Box }^+}) $
:
(3.12) $$ \begin{align} F^{r+1}\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} })\to F^r\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} })\stackrel{\beta_X}{\to} \bigoplus_{i\leq r}\mathrm{R}\Gamma_c(X,\Omega^i_X)(r-i)[-i]. \end{align} $$
Proof. The proposition follows from Proposition 3.6, applying it to the smooth varieties X and
$X \setminus Z$
, for Z quasi-compact. As usual, we use that the solid tensor product commutes with colimits for the first claim. The second and third points come from the fact that, by definition, we have distinguished triangles in
${\mathscr D}({{\mathbf B}_{\mathrm {dR} ,\Box }^+}) $
and in
${\mathscr D}(C_{\Box })$
, respectively:
3.1.4. Computations
In this section, we will give an explicit formula to compute the quotients of the compactly supported
${\mathbf B}_{\mathrm {dR} }^+$
-cohomology of X when X is a Stein variety (and in particular, when X is the affine space). These quotients will intervene in the computation of the compactly supported pro-étale cohomology of X, and the following results will allow us to define a trace map for the compactly supported pro-étale cohomology in Section 7.3.
(i) Stein varieties. Let X be a smooth Stein variety of dimension d over K. We will see later that in that case
$H^i_c(X, \Omega ^j_X)=0$
for
$i \neq d$
and all j in
$\{0, \ldots , d\}$
(see Proposition 5.10). Thus, we obtain that the de Rham cohomology
$\mathrm {R}\Gamma _{\mathrm {dR} ,c}(X)$
is computed by the complex:
It follows that in
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
:
Concerning the filtration, we have in
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
![F^r (R Gamma d R, c (X) tensor K B+ d R) is isomorphic to colim i+j >= r F^i H^d c (X, Omega dot X) tensor K F^j B+ d R, which is isomorphic to (H^d c (X, O X) tensor K F^r B+ d R arrow H^d c (X, Omega^1 X) tensor K F^r-1 B+ d R arrow ...) [-d].](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu128.png?pub-status=live)
This yields in
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
![D R sub c (X, r) is defined as (R Gamma sub d R, c (X) tensor over K B super + sub d R) / F super r. This is isomorphic to a complex starting with (H sub c super d (X, O sub X) tensor over K (B super + sub d R / F super r)) and ending in [-d].](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu129.png?pub-status=live)
Lemma 3.14.
-
1. We have an exact sequence in ${\mathbf B}^+_{\mathrm {dR} ,\Box }$
: 
-
2. In degree $2d$
, we have an isomorphism in
${\mathbf B}^+_{\mathrm {dR} ,\Box }$
: 
Proof. This follows from the fact that, for
$0 \le j\le d$
, the differential
$\tilde {d}_{j+d}$
of the complex
$\mathrm {DR} _c(X,r)$
factorizes as
where the first arrow is surjective with kernel
.
(ii) Affine space. For example, let
$X={\mathbb A}_K^d$
be the rigid analytic affine space over K of dimension
$d\geq 1$
. We will see in Section 5 that we have
Lemma 3.16. Let
$r^{\prime }:=r-i+d-1$
. We have isomorphisms in
${\mathbf B}^+_{\mathrm {dR} ,\Box }$
:
We note that
$( H_c^d(X_C, \Omega ^{i-d})/\mathrm {Im}\, d) \otimes ^{\Box }_F\mathrm {gr}^{r^{\prime }}{\mathbf B}^+_{\mathrm {dR} }\simeq ( H_c^d(X_C, \Omega ^{i-d})/\mathrm {Ker}\, d )\otimes ^{\Box }_F\mathrm {gr}^{r^{\prime }}{\mathbf B}^+_{\mathrm {dR} } $
.
3.2. Rigid analytic Hyodo–Kato cohomology with compact support
We now define the Hyodo–Kato cohomology with compact support for smooth rigid analytic varieties over
$K,C$
. The construction is as in Section 2.1, using the definitions of [Reference Colmez and Nizioł14], [Reference Colmez and Nizioł15] of the rigid analytic Hyodo–Kato cohomologies. We then prove, using the classical case, that we have a compactly supported version of the Hyodo–Kato (iso)morphisms.
3.2.1. Definition
We will give three definitions of Hyodo–Kato cohomologies: the arithmetic one (when the variety is defined over K) and the geometric and completed ones (when the variety is defined over C).
(i) Rigid analytic Hyodo–Kato cohomology. Let
$L=K,C$
and
$X \in \mathrm {Sm}_L$
. As in Section 3.1.2 (i.e., by regarding the crystalline sheaves as sheaves with values in the solid world), we can define the solid versions of the Hyodo–Kato cohomologies from [Reference Colmez and Nizioł14, Section 4.2 and Section 4.3]:
and, if
$X \in \mathrm {Sm}_C$
, the completed Hyodo–Kato cohomology (see [Reference Colmez and Nizioł15, §4.1.1]):
Here,
${\mathscr {D}}_{\varphi ,N} (-) $
denotes the derived
$\infty $
-category of solid
$(\varphi , N)$
-modules; similarly, we define the category
${\mathscr D}_{\varphi ,N,{\mathscr {G}}_K}(-)$
.
Lemma 3.17. For any
$X \in \mathrm {Sm}_C$
, we have a canonical quasi-isomorphism in
${\mathscr D}_{\varphi ,N} (\breve {F}_{\Box })$
:
Proof. We can work étale locally. Let
${\mathscr {X}}$
be the base change of a formal model
${\mathscr {X}}_{{\mathscr {O}}_L}$
defined over L a finite extension of K. We have a quasi-isomorphism:
where
${\mathscr {O}}_{F_L}:=W(k_L)$
. By taking the derived inverse limit over n and inverting p, we get a quasi-ismorphism:
where
$\widehat {\otimes }^{\mathrm {L}}$
is the derived completion. Since
$ \mathrm {R}\Gamma _{\mathrm {HK} }({\mathscr {X}}_0) $
is built from Banach spaces, we can pass to the solid tensor product.
(ii) Compactly supported Hyodo–Kato cohomology. Proceeding as in Section 2.1, we obtain compactly supported Hyodo–Kato cohomology
$\mathrm {R}\Gamma _{\mathrm {HK} ,c}(X)$
from
$\mathrm {R}\Gamma _{\mathrm {HK} }(X)$
. This is a solid dg F-algebra if
$L=K$
, and a dg
$F^{\mathrm {nr} }$
-algebra if
$L=C$
, equipped with a Frobenius
$\varphi $
, a monodromy operator N, and a continuous action of
${\mathscr {G}}_K$
if X is defined over K. It satisfies all of the properties in Section 2.1.
If
$X \in \mathrm {Sm}_C$
, we define as above its completed version
$\mathrm {R}\Gamma _{\mathrm {HK} ,\breve {F},c}(X)$
, using
$\mathrm {R}\Gamma _{\mathrm {HK} ,\breve {F}}(X)$
. It is a solid dg
$\breve {F}$
-algebra equipped with a Frobenius
$\varphi $
, a monodromy operator N, and a continuous action of
${\mathscr {G}}_K$
if X is defined over K. It satisfies all of the properties in Section 2.1. Moreover, since the tensor product commutes with colimits, the quasi-isomorphism from Lemma 3.17 applied to
$X, X\setminus Z$
, for Z quasi-compact, induces a quasi-isomorphism in
${\mathscr {D}}_{\varphi ,N} (\breve {F}_{\Box })$
:
3.2.2. Hyodo–Kato morphisms
We will define two types of Hyodo–Kato morphisms: Hyodo–Kato-to-de Rham and Hyodo–Kato-to-
${\mathbf B}^+_{\mathrm {dR} }$
. Recall the result for usual cohomology.
Proposition 3.18 [Reference Colmez and Nizioł15, Theorem 4.6].
For
$X \in \mathrm {Sm}_C$
, we have natural quasi-isomorphisms in
${\mathscr D}(C_{\Box })$
and
${\mathscr {D}}({{\mathbf B}^+_{\mathrm {dR} ,\Box }})$
, respectively,
where
$F_L=F^{\mathrm {nr} }, \breve {F}$
, and
$*=-, \breve {F}$
, that are compatible with the maps
$\theta : {\mathbf B}_{\mathrm {dR} }^+ \to C$
and
$\vartheta $
from (3.7).
Proof. We can work étale locally. The local quasi-isomorphisms are constructed in [Reference Colmez and Nizioł15] and the construction goes through in the condensed setting. Recall that the main point is to show that we have a quasi-isomorphism:
We deduce the following proposition.
Proposition 3.19. Let X be a smooth rigid analytic variety over
$L=K,C$
.
-
1. There is a Hyodo–Kato morphism in ${\mathscr {D}}(F_{L,\Box })$
$$ \begin{align*}\iota_{\mathrm{HK} ,c}: \quad \mathrm{R}\Gamma_{\mathrm{HK} ,*,c}(X){\to}\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X) \end{align*} $$
(where $*=-, \breve {F}$
) that is compatible with its usual version
$ \iota _{\mathrm {HK} }: \mathrm {R}\Gamma _{\mathrm {HK} ,*}(X){\to }\mathrm {R}\Gamma _{\mathrm {dR} }(X). $
-
2. If $L=C$
, it induces quasi-isomorphisms in
${\mathscr D}(C_{\Box })$
and in
${{\mathbf B}^+_{\mathrm {dR} ,\Box }}$
, respectively: 
where $F_L=F^{\mathrm {nr} }, \breve {F}$
and
$*=-, \breve {F}$
, that are compatible with the maps
$\theta : {\mathbf B}_{\mathrm {dR} }^+ \to C$
and
$\vartheta _c$
from (3.10).
Proof. The proposition follows immediately from Proposition 3.18 applied to
$Y=X, X\setminus Z$
, for Z quasi-compact.
4. Overconvergent de Rham and Hyodo–Kato cohomologies with compact support
In this section, we define compactly supported de Rham,
${\mathbf B}_{\mathrm {dR} }^+$
-, and Hyodo–Kato cohomologies for smooth dagger varieties over
$L=K,C$
. To do that, we first define the compactly supported cohomology of a dagger affinoid X as the colimit of the cohomologies of the rigid affinoids
$X_h$
forming a presentation of the dagger structure, but supported in the rigid completion
$\widehat {X}$
of X. We then globalize this definition.
We prove various properties satisfied by these cohomologies, which are, as before, compactly supported versions of the results from [Reference Colmez and Nizioł14], [Reference Colmez and Nizioł15]. In particular, we compare them with their rigid analytic analogs defined in the previous section.
4.1. Definition of de Rham cohomology with compact support
We first introduce the definition of overconvergent de Rham cohomology with compact support using presentations of dagger structures (see [Reference Colmez and Nizioł14, §3.2.1] and [Reference Vezzani31, Appendix] for the definition and properties of presentations of dagger structures).
(i) Local definition. Let X be a dagger affinoid over
$L=K,C$
. Let
$\mathrm {pres}(X)=\{X_h\}$
and let
$\widehat {X}$
be the rigid completion of X. Define in
${\mathscr D}(L_{\Box })$
:
where
$\mathrm {R}\Gamma ^{\natural }_{\mathrm {dR} }(X):= \mathrm {colim} _h \mathrm {R}\Gamma _{\mathrm {dR} }(X_h)$
is the overconvergent de Rham cohomology from [Reference Colmez and Nizioł15]. We have a natural filtration on
$\mathrm {R}\Gamma ^{\natural }_{\mathrm {dR} ,c}(X)$
:
We can write
As in the pro-étale case, this makes it clear that the functor
$F^r\mathrm {R}\Gamma ^{\natural }_{\mathrm {dR} ,c}(X)$
is covariant for open embeddings.
(ii) Globalization. For a general smooth dagger variety X over L, using the natural equivalence
we define the cosheavesFootnote
8
${\mathscr {A}}_{\mathrm {dR} ,c}$
and
$F^r{\mathscr {A}}_{\mathrm {dR} ,c}$
,
$r\ge 0$
, on
$X_{\mathrm {an}}$
with values in
${\mathscr D}(L_{\Box })$
as the cosheaves associated with the precosheaves defined by
$U\mapsto \mathrm {R}\Gamma ^{\natural }_{\mathrm {dR} ,c}(U)$
and
$U\mapsto F^r\mathrm {R}\Gamma ^{\natural }_{\mathrm {dR} ,c}(U)$
,
$r \ge 0$
, for
$U\in \mathrm {SmAff}^{\dagger }_{L}$
,
$U\subset X$
an admissible open. We set
We obtain a solid filtered dg L-algebra.
-
1. (Local–global compatibility) If X is a smooth dagger affinoid over $L=K,C$
, there is a quasi-isomorphism in
${\mathscr {F}}{\mathscr D}(L_{\Box })$
: $$\begin{align*}\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X) \stackrel{\sim}{\to} \mathrm{R}\Gamma^{\natural}_{\mathrm{dR} ,c}(X). \end{align*}$$
-
2. (Passing to completion) If X is smooth and partially proper over $L=K,C,$
then there is a natural quasi-isomorphism in
${\mathscr {F}}{\mathscr D}(L_{\Box })$
$$ \begin{align*}\mathrm{R}\Gamma_{\mathrm{dR} ,c}({X})\stackrel{\sim}{\to} \mathrm{R}\Gamma_{\mathrm{dR} ,c}(\widehat{X}). \end{align*} $$
Proof. The proof of this lemma is analogous to the one of Lemma 2.34.
Proposition 4.4. Let X be a smooth dagger Stein variety over
$L=K,C$
and let
$\{U_n\}_{n}$
be an admissible strict covering of X with dagger affinoids
$U_n \Subset U_{n+1}$
. Then there are natural quasi-isomorphisms in
${\mathscr {D}}(L_{\Box })$
:
Remark 4.5. In particular, if we define the cohomology of the boundary of X from Proposition 4.4 as
we have a distinguished triangle:
as in the rigid analytic set-up.
Proof. Let X and
$\{U_n\}$
be as in the statement of the proposition. For each n, let
$\{U_{n,h} \}_h$
be a presentation of
$U_n$
. Then,
where the first quasi-isomorphism comes from the fact that
${\mathscr {A}}_{\mathrm {dR} ,c}$
is a cosheaf, the second one is the local–global compatibility from Lemma 4.3, and the third one is the de Rham analog of the one from Proposition 2.36. For
$h \in \mathbf {N}$
, from the excision (2.1), we have
We conclude the proof using the quasi-isomorphisms
$\mathrm {R}\Gamma _{\mathrm {dR} }(\widehat {X})\xleftarrow {\sim }\mathrm {R}\Gamma _{\mathrm {dR} }(X)$
and
$\mathrm {R}\Gamma _{\mathrm {dR} }(\widehat {X}\setminus \widehat {U}_n)\xleftarrow {\sim }\mathrm {R}\Gamma _{\mathrm {dR} }(X \setminus U_n)$
.
4.2. Overconvergent
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology with compact support
Proceeding as for the de Rham cohomology, we define compactly supported
${\mathbf B}_{\mathrm {dR} }^+$
-cohomology via presentation of dagger structures.
4.2.1. Definition
Let X be a smooth dagger affinoid over C. Taking a presentation
$\mathrm {pres}(X)=\{X_h\}$
of X as above, we define overconvergent
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology with compact support
using the overconvergent
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology
from [Reference Colmez and Nizioł14, §3.4.1]. The functor
$ F^r\mathrm {R}\Gamma ^{\natural }_{\mathrm {dR} ,c}(X/{\mathbf B}^+_{\mathrm {dR} }) $
is covariant for open embeddings.
The
$\eta $
-analytic cosheafification of
$ F^r\mathrm {R}\Gamma ^{\natural }_{\mathrm {dR} ,c}(X/{\mathbf B}^+_{\mathrm {dR} })$
gives us a cosheaf
$F^r{\mathscr {A}}^{\underset {\widehat {\phantom {\ \ }}}{\phantom {\_}}}_{\mathrm {cr} ,c}$
on any smooth dagger variety X over C, with values in
${\mathscr D}({\mathbf B}_{\mathrm {dR} ,\Box }^+)$
. The filtered
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology with compact support is then defined as
-
1. (Local–global compatibility) If X is a smooth dagger affinoid over C, there is a quasi-isomorphism in ${\mathscr {F}}{\mathscr D}({{\mathbf B}_{\mathrm {dR} ,\Box }^+})$
: $$\begin{align*}\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} }) \stackrel{\sim}{\to} \mathrm{R}\Gamma^{\natural}_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} }). \end{align*}$$
-
2. (Passing to completion) If X is smooth and partially proper over C, then there is a natural quasi-isomorphism in ${\mathscr {F}}{\mathscr D}({{\mathbf B}_{\mathrm {dR} ,\Box }^+})$
: $$ \begin{align*}\mathrm{R}\Gamma_{\mathrm{dR} ,c}({X}/{\mathbf B}^+_{\mathrm{dR} })\stackrel{\sim}{\to} \mathrm{R}\Gamma_{\mathrm{dR} ,c}(\widehat{X}/{\mathbf B}^+_{\mathrm{dR} }). \end{align*} $$
Proof. The proof of this lemma is analogous to the one of Lemma 2.34.
We have an analog of Proposition 4.4 in this setting (using [Reference Colmez and Nizioł15, Corollary 4.32]), hence, we see that if X is Stein and smooth, we have a distinguished triangle
where
$ \mathrm {R}\Gamma _{\mathrm {dR} }(\partial X/ {\mathbf B}_{\mathrm {dR} }^+):= \mathrm {colim} _{n} \mathrm {R}\Gamma _{\mathrm {dR} }((X \setminus U_n)/ {\mathbf B}_{\mathrm {dR} }^+)$
, for
$\{U_n\}$
a Stein covering of X.
4.2.2. Properties
We will now prove properties of overconvergent
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology that do not require Hyodo–Kato cohomology. We have canonical maps in
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
and
${\mathscr {F}}{\mathscr {D}}(K_{\Box })$
, respectively:
induced by their rigid analytic analogs.
Proposition 4.9.
-
1. (Projection) Let X be a smooth dagger variety over C. Then,
-
(a) The map $\vartheta _c$
yields a natural quasi-isomorphism in
${\mathscr D}(C_{\Box })$
: 
-
(b) More generally, for $r\geq 0$
, we have a natural distinguished triangle in
${\mathscr D}({{\mathbf B}_{\mathrm {dR} ,\Box }^+}) $
: (4.10)
-
(c) (Devissage) For $r\geq 0$
, we have a natural distinguished triangle in
$ {\mathscr D}({{\mathbf B}_{\mathrm {dR} ,\Box }^+}) $
: (4.11) $$ \begin{align} F^{r+1}\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} })\to F^r\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} })\to \bigoplus_{i\leq r}\mathrm{R}\Gamma_c(X,\Omega^i_X)(r-i)[-i]. \end{align} $$
-
-
2. (Product formula) Let X be a smooth dagger variety over K. The map $\iota _{\mathrm {BK},c}$
defined above yields a natural quasi-isomorphism in
${\mathscr {F}}{\mathscr D}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
: 
Remark 4.12. In Proposition 4.9(2), the filtration on
is defined by the formula
and, if X is a dagger affinoid, we also define
Note that we have a local–global compatibility between the two, using Lemma 4.3. By the same argument as in Remark 3.2, we see that we have a distinguished triangle
We also have
, for
$\{ X_h\}$
a dagger presentation of X.
Proof. To prove the point (1)(a) of the proposition, it suffices to argue locally, then apply the analogous quasi-ismorphism obtained in the rigid analytic case (3.7) to the varieties
$X_h$
and
$X_h \setminus \widehat {X}$
and we conclude using that the solid tensor product commutes with colimits.
The arguments are similar for the distinguished triangles (1)(b) (using (3.8)) and (1)(c) (using (3.9)), and for the quasi-isomorphism (2) (using (3.3) and the previous remark for the compatibility with the filtrations).
4.3. Overconvergent Hyodo–Kato cohomology with compact support
We now define overconvergent Hyodo–Kato cohomologies with compact support via similar methods. As before, we have three definitions (the arithmetic Hyodo–Kato cohomology, if
$X \in \mathrm { Sm}_K^{\dagger }$
, and the geometric and completed ones, if X is defined over C). We will obtain Hyodo–Kato (iso)morphisms, compatible with the maps from the above proposition.
4.3.1. Definition
Let
$L=K,C$
and X be a smooth dagger affinoid variety over L. Starting from the overconvergent Hyodo–Kato cohomologies
from [Reference Colmez and Nizioł15, §4.2.1] we obtain, as in the de Rham case, the local compactly supported Hyodo–Kato cohomologies:
and, if X is over C, the completed Hyodo–Kato cohomology:
These functors are covariant for open embeddings.
This allows us to define cosheaves
${\mathscr {A}}_{\mathrm {HK} ,c}$
and
${\mathscr {A}}_{\mathrm {HK} ,\breve {F},c}$
on any smooth dagger variety X over L. We define
It is a solid dg
$F_L$
-algebra equipped with a Frobenius, monodromy action, and a continuous action of
${\mathscr {G}}_K$
if X is defined over K. If X is Stein, we have a distinguished triangle
where
$*=-,\breve {F}$
and
$\mathrm {R}\Gamma _{\mathrm {HK} ,*}(\partial X):= \mathrm {colim} _n \mathrm {R}\Gamma _{\mathrm {HK} ,*}(X\setminus U_n)$
, for a Stein covering
$\{U_n\}$
.
Lemma 4.14. For any
$X \in \mathrm {Sm}^{\dagger }_C$
, we have a canonical quasi-isomorphism in
${\mathscr D}_{\varphi ,N}({\breve {F}}_{\Box })$
:
Proof. We can work locally. Let X be a smooth dagger affinoid over C. Then,
![R Gamma natural H K comma c (X) tensor L box F L check F equals colim h [R Gamma H K (X h) arrow R Gamma H K (X h minus X hat)] tensor L box F L check F. This maps to colim h [R Gamma H K (X h) tensor check F arrow R Gamma H K (X h minus X hat) tensor check F].](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu169.png?pub-status=live)
where
$F_L=\mathrm {Frac}(W(k_L))$
. The first quasi-isomorphism is obtained by commutativity of the solid tensor product with colimits, and the second one is the map
$\beta $
from Lemma 3.17.
4.3.2. Overconvergent Hyodo–Kato morphisms
Let X be a smooth dagger affinoid over K or C. The rigid analytic Hyodo–Kato morphism from Section 3.2.2 induces a morphism:
coming from the commutative diagram:

where
$\{X_h\}$
is the presentation of X,
$\widehat {X}$
—the rigid analytic completion of X, and
$*=-, \breve {F}$
.
Let X be a smooth dagger variety over K or C. The previous morphism
$\iota _{\mathrm {HK} }^{\natural }$
is clearly functorial for open immersions hence globalizes to give a morphism
compatible with its classical version
$\iota _{\mathrm {HK} }: \mathrm {R}\Gamma _{\mathrm {HK} ,*}(X){\to }\mathrm {R}\Gamma _{\mathrm {dR} }(X).$
Proposition 4.15. Let X be a smooth dagger variety over C. The Hyodo–Kato morphism
$\iota _{\mathrm {HK} ,c}$
induces quasi-isomorphisms (where
$F_L=F^{\mathrm {nr} }, \breve {F}$
and
$*=-, \breve {F}$
) in
${\mathscr {D}}(C_{\Box })$
and
${\mathscr {D}}({{\mathbf B}^+_{\mathrm {dR} ,\Box }})$
, respectively:
that are compatible with the maps
$\theta : {\mathbf B}_{\mathrm {dR} }^+ \to C$
and
$\vartheta _c$
from Section 4.2.2.
Proof. It suffices to argue locally. Let X be a smooth dagger affinoid over L. Then,
![Equation showing R Gamma natural H K asterisk c (X) tensor L square F L C equals colim h [R Gamma H K asterisk (X h) arrow R Gamma H K asterisk (X h minus X hat)] tensor L square F L C, which maps to R Gamma natural d R c (X).](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu174.png?pub-status=live)
The first quasi-isomorphism is obtained by commutativity of the solid tensor product with colimits, and the second one is the Hyodo–Kato morphism from Proposition 3.18.
As an immediate application of the overconvergent Hyodo–Kato quasi-isomorphisms, we get the local–global compatibility for (geometric and completed) Hyodo–Kato and
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology with compact support.
Corollary 4.16 (Local–global compatibility).
Let X be a smooth dagger affinoid over C.
-
1. There is a natural quasi-isomorphism in ${\mathscr {D}}_{\varphi ,N}(F_{L,\Box })$
: $$ \begin{align*} \mathrm{R}\Gamma_{\mathrm{HK} ,*,c}(X) \to \mathrm{R}\Gamma^{\natural}_{\mathrm{HK} ,*,c}(X), \end{align*} $$
where $*=-,\breve {F}$
. -
2. The canonical morphism in ${\mathscr {F}}{\mathscr {D}}({{\mathbf B}^+_{\mathrm {dR} ,\Box }})$
$$ \begin{align*} \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} })\to \mathrm{R}\Gamma^{\natural}_{\mathrm{dR} ,c}(X/{\mathbf B}^+_{\mathrm{dR} }) \end{align*} $$
is a quasi-isomorphism.
Proof. We start with the proof for the Hyodo–Kato cohomology. The proof is the same as [Reference Colmez and Nizioł15, Proposition 3.5]. It suffices to show that, for any analytic dagger affinoid hypercovering
$U_{\bullet }$
of X, the map
is a quasi-isomorphism. Consider the following commutative diagram (where
$F_L=F^{\mathrm {nr}}, \breve {F}$
and
$*=-, \breve {F}$
) in
${\mathscr {D}}(C_{\Box })$
:

The vertical arrows are quasi-isomorphisms by (the proof of) Proposition 4.15 and the bottom horizontal one by (the proof of) Lemma 4.3. It follows that the upper horizontal arrow is a quasi-isomorphism as well.
It remains to check that this implies the quasi-isomorphism (4.17). For that, it is enough to show that if
$K^{\bullet }$
is in
${\mathscr D}({F_{1,\Box }})$
, for
$F_1=\breve {F}$
or a finite unramified extension of F, such that
is acyclic then
$K^{\bullet }$
itself is acyclic. To see that, writing
$C \simeq F_1 \oplus W$
with W an
$F_1$
-Banach space, we obtain
so
$H^*(K^{\bullet })=0$
, and this concludes the proof of the first point.
The second point follows from the first one, and from Lemma 4.3, by the exact same argument as in [Reference Colmez and Nizioł15, Corollary 4.28].
4.4. Comparison with the rigid analytic constructions
We can now compare the overconvergent compactly supported cohomologies with the rigid analytic ones. Let X be a smooth dagger variety over
$L=K,C$
and let
$\widehat {X}$
be its completion. Then, we have the following proposition.
Proposition 4.18. Assume that X is partially proper. Then,
-
1. There is a natural quasi-isomorphim in ${\mathscr {D}}_{\varphi ,N}(*_{\Box })$
, for
$*=F, F^{\mathrm {nr} }$
, respectively
$:$
(4.19) $$ \begin{align} \mathrm{R}\Gamma_{\mathrm{HK} ,c}({X})\xrightarrow{\sim} \mathrm{R}\Gamma_{\mathrm{HK} ,c}(\widehat{X}). \end{align} $$
-
2. Let $L=C$
. There are compatible natural quasi-isomorphisms in
${\mathscr {D}}_{\varphi ,N}(\breve {F}_{\Box })$
and
${\mathscr {F}}{\mathscr {D}}({{\mathbf B}^+_{\mathrm {dR} ,\Box }})$
, respectively
$\!\textit{:}$
$$ \begin{align*} \mathrm{R}\Gamma_{\mathrm{HK} ,\breve{F},c}({X})\xrightarrow{\sim}\mathrm{R}\Gamma_{\mathrm{HK} ,\breve{F},c}(\widehat{X}),\quad \mathrm{R}\Gamma_{\mathrm{dR} ,c}({X}/{\mathbf B}^+_{\mathrm{dR} })\xrightarrow{\sim}\mathrm{R}\Gamma_{\mathrm{dR} ,c}(\widehat{X}/{\mathbf B}^+_{\mathrm{dR} }). \end{align*} $$
They are compatible with the map (4.19).
-
3. The morphisms in (1) and (2) are compatible with the Hyodo–Kato morphisms, that is, we have the commutative diagrams (where $*=-, \breve {F}$
) in
${\mathscr {D}}(F_{L,\Box })$
and
${\mathscr {D}}(\breve {F}_{\Box })$
, respectively
$:$

5. Dualities for de Rham and Hyodo–Kato cohomologies
We prove Poincaré duality results for the de Rham and Hyodo–Kato cohomologies of partially proper smooth rigid analytic varieties over
$L=K,C$
. The de Rham duality will follow from the coherent duality theorem for smooth Stein varieties first proved by Chiarellotto in [Reference Chiarellotto6]. We then obtain the same results for quasi-compact smooth dagger varieties over K or C. In the dagger affinoid case, the coherent and de Rham dualities were shown by Grosse-Klönne in [Reference Grosse-Klönne18, Theorems 4.4 and 4.9].
The trace maps constructed below will allow us to define a trace map for p-adic pro-étale cohomology in Section 7.3. This trace morphism will then be used in [Reference Colmez, Gilles and Nizioł10] to prove Poincaré duality for p-adic pro-étale cohomology of rigid analytic varieties.
5.1. Coherent duality: Classical approach
We will briefly review the classical coherent dualities for rigid analytic varieties.
5.1.1. Rigid analytic setting
Let
$L=K,C$
and let X be a rigid analytic variety over L. In this section, we will discuss the following well-known result. We work in the category of locally convex topological vector spaces over L.
Theorem 5.1 (Serre duality).
Let X be a Stein or a proper rigid analytic variety, smooth of dimension d over L. Then,
-
1. There exists a canonical trace map $\mathrm {tr}_{\mathrm {coh}}: \, H_c^{d}(X, \Omega _X^d)\to L$
. -
2. For all coherent sheaves ${\mathscr {F}}$
on X, the pairings $$ \begin{align*} & H_c^i(X, {\mathscr{F}}) \times \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X}({\mathscr{F}},\Omega_X^{d}) \to H_c^{d}(X, \Omega_X^d) \xrightarrow{\mathrm{tr}_{\mathrm{coh}}} L \\ & H^i(X, {\mathscr{F}}) \times \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X,c}({\mathscr{F}},\Omega_X^{d}) \to H_c^{d}(X,\Omega_X^d) \xrightarrow{\mathrm{tr}_{\mathrm{coh}}} L \end{align*} $$
induce perfect dualities, that is, we have the induced isomorphisms:
$$ \begin{align*} & \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X}({\mathscr{F}},\Omega_X^{d}) \stackrel{\sim}{\to} {\mathrm{Hom}} _L(H_c^i(X, {\mathscr{F}}),L) & \text{ and } & & H_c^i(X, {\mathscr{F}}) \stackrel{\sim}{\to} {\mathrm{Hom}} _L( \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X}({\mathscr{F}},\Omega_X^{d}),L), \\ & \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X,c}({\mathscr{F}},\Omega_X^{d}) \stackrel{\sim}{\to} {\mathrm{Hom}} _L(H^i(X, {\mathscr{F}}),L) & \text{ and } & & H^i(X, {\mathscr{F}}) \stackrel{\sim}{\to} {\mathrm{Hom}} _L( \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X,c}({\mathscr{F}},\Omega_X^{d}),L). \end{align*} $$
This result was proved for smooth Stein varieties over C by Chiarellotto in [Reference Chiarellotto6]. This was then extended by van der Put to include proper rigid analytic varieties over L in [Reference van der Put30]. A different proof for smooth Stein varieties over L was given by Beyer in [Reference Beyer4]. In the following, we will recall the strategy of the proof of [Reference Chiarellotto6], [Reference van der Put30] and in the next section, we will reformulate their main results in the condensed setting.
(i) Duality for the affine space. Let
${\mathbb A}^d_L$
be the rigid affine space of dimension d over L. Cover
${\mathbb A}^d_L$
with the discs:
and recall that the compactly supported cohomology of
$\Omega ^d$
can be computed using the distinguished triangle:
Lemma 5.3. We have
$H^i_c({\mathbb A}^d_L, \Omega ^d)=0$
for
$i \neq d$
and for
$i=d$
:
where
$\nu =(\nu _1, \ldots , \nu _d) \in \mathbf {Z}^d$
and
$x^{\nu }=x_1^{\nu _1}x_2^{\nu _2} \dots x_d^{\nu _d}$
.
Proof. The result follows from the long exact sequence (5.2) using that we have
$H^i({\mathbb A}_L^d, \Omega ^d) = 0$
, for
$i \neq 0$
, and
To prove the latter formula, consider the admissible covering of
${\mathbb A}_L^d\setminus D_j$
by the open subsets
$\{U_i\}_{1 \le i \le d}$
, where
and use the associated Čech cohomology.
We define the trace map for the affine space as
where
$\nu =(\nu _1, \ldots , \nu _d) \in \mathbf {Z}^d$
,
$x^{\nu }=x_1^{\nu _1}x_2^{\nu _2} \dots x_d^{\nu _d}$
, and
$dx:=dx_1 \wedge \cdots \wedge dx_d$
.
Proposition 5.5 [Reference van der Put30, Lemma 2.5 and Prop. 2.6].
Theorem 5.1 is true for
$X={\mathbb A}_L^d$
.
Proof. The trace map is given by formula (5.4).
First, assume that
${\mathscr {F}}= {\mathscr {O}}_X$
. For
$i \neq d$
, both terms of the product are zero, so the pairing is perfect. For
$i=d$
, the pairing is given by
and it induces a perfect duality. This proves the proposition for
${\mathscr {F}}= {\mathscr {O}}_X$
and we can deduce from it the result, first, for
${\mathscr {F}}= {\mathscr {O}}_X^m$
and then for a general coherent sheaf.
(ii) Duality for Stein varieties. We can now deduce from the previous proposition the duality result for general smooth Stein varieties. Assume that X is Stein and choose a closed immersion
$i: X \hookrightarrow {\mathbb A}^N_L$
. We have the following classical results.
Lemma 5.6 [Reference Chiarellotto6, Equation (4.15)].
There is a canonical quasi-isomorphism
$\Omega _X^d[d-N] \simeq \mathrm {R} i^{!}\Omega _{{\mathbb A}^N_L}^N$
.
-
1. There is a canonical quasi-isomorphism $i_*\Omega _X^d[d-N] \simeq \mathrm {R}{\mathrm {Hom}} _{{\mathscr {O}}_{{\mathbb A}_L^N}}(i_* {\mathscr {O}}_X, \Omega _{{\mathbb A}^N_L}^N)$
. -
2. For all coherent sheaves ${\mathscr {F}}$
on X, there is a canonical isomorphism
$H_c^i(X, {\mathscr {F}}) \xrightarrow {\sim } H_c^i({\mathbb A}_L^N, i_*{\mathscr {F}})$
, for all
$i \ge 0$
. -
3. For all coherent sheaves ${\mathscr {F}}$
on X, there is a canonical quasi-isomorphism $$ \begin{align*}\mathrm{R}{\mathrm{Hom}} _{{\mathscr{O}}_X}({\mathscr{F}}, \Omega_X^d)[d-N] \xrightarrow{\sim} \mathrm{R}{\mathrm{Hom}} _{{\mathscr{O}}_{{\mathbb A}^N_L}}(i_*{\mathscr{F}}, \Omega_{{\mathbb A}_L^N}^N).\end{align*} $$
Proof. The first claim follows from Lemma 5.6 using the fact that
$i^{!}$
is right adjoint to
$i_*$
.
To prove claim (2), note that the result is true for the usual cohomology (without compact support). We deduce the isomorphism for the compactly supported cohomology using that for each open affinoid V of X, we can find a finite set of open affinoids
$Z_1, \ldots , Z_n$
in the affine space such that V is the intersection of the
$Z_i$
’s with X (see [Reference Chiarellotto6, Prop. 4.17]).
For the third claim, consider an injective resolution
${\mathscr {I}}_{\bullet }$
of
$\Omega _{{\mathbb A}_L^N}^N$
. Then
We conclude using that the functor
$i^!$
sends injectives to injectives and applying Lemma 5.6.
We define the trace map for a smooth Stein variety X as the composition:
where the first and second isomorphisms follow from the previous lemma and the third one from the duality for the affine space.
Lemma 5.8 [Reference van der Put30, Th. 3.5 and Th. 3.7].
Let X be a smooth Stein variety over L, of dimension d. Then,
-
1. The trace map does not depend of the chosen closed immersion $X \hookrightarrow {\mathbb A}^N_L$
. -
2. If $X \to Y$
is an open immersion of smooth Stein varieties over L of dimension d, the composition $$\begin{align*}H^d_c(X, \Omega^d) \to H^d_c(Y, \Omega^d) \xrightarrow{\mathrm{tr}_{\mathrm{coh},Y}} L \end{align*}$$
is equal to $\mathrm {tr}_{\mathrm {coh},X}: H^d_c(X, \Omega ^d) \to L$
.
Proposition 5.9. Theorem 5.1 is true for smooth Stein varieties.
Proof. Let X be a smooth Stein variety. Our theorem follows from the duality for the affine space (Proposition 5.5) using the isomorphisms from Corollary 5.7:
In particular, we obtain the following proposition.
Proposition 5.10. Let X be a smooth Stein variety of dimension d over L, and let
${\mathscr {F}}$
be a locally free sheaf on X. Then
$H^i_c(X, {\mathscr {F}})=0$
if
$i \neq d$
.
5.1.2. Overconvergent setting
In the dagger case, the coherent duality was studied by Grosse-Klönne. We will review it briefly.
Theorem 5.11 [Reference Grosse-Klönne18, Theorem 4.4].
Let X be smooth dagger affinoid of dimension d over L. Then,
-
1. There exists a canonical trace map $\mathrm {tr}_{\mathrm {coh}}: \, H_c^{d}(X, \Omega _X^d)\to L$
. -
2. For all coherent sheaves ${\mathscr {F}}$
on X, the pairings $$ \begin{align*} & H_c^i(X, {\mathscr{F}}) \times \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X}({\mathscr{F}},\Omega_X^{d}) \to H_c^{d}(X, \Omega_X^d) \xrightarrow{\mathrm{tr}_{\mathrm{coh}}} L \\ & H^i(X, {\mathscr{F}}) \times \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X,c}({\mathscr{F}},\Omega_X^{d}) \to H_c^{d}(X, \Omega_X^d) \xrightarrow{\mathrm{tr}_{\mathrm{coh}}} L \end{align*} $$
induce perfect dualities, that is, we have the induced isomorphisms of L-vector spaces:
$$ \begin{align*} & \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X}({\mathscr{F}},\Omega_X^{d}) \stackrel{\sim}{\to} {\mathrm{Hom}} _L(H_c^i(X, {\mathscr{F}}),L) & \text{ and } & & H_c^i(X, {\mathscr{F}}) \stackrel{\sim}{\to} {\mathrm{Hom}} _L( \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X}({\mathscr{F}},\Omega_X^{d}),L), \\ & \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X,c}({\mathscr{F}},\Omega_X^{d}) \stackrel{\sim}{\to} {\mathrm{Hom}} _L(H^i(X, {\mathscr{F}}),L) & \text{ and } & & H^i(X, {\mathscr{F}}) \stackrel{\sim}{\to} {\mathrm{Hom}} _L( \mathrm{Ext}^{d-i}_{{\mathscr{O}}_X,c}({\mathscr{F}},\Omega_X^{d}),L). \end{align*} $$
The proof is similar to the one in the rigid case. We will first prove the result for
$X:=\mathrm {Sp}(L[X_1, \ldots , X_d]^{\dagger })$
and then consider a closed immersion
$i: X \hookrightarrow \mathrm {Sp}(L[X_1, \ldots , X_N]^{\dagger })$
to deduce the duality for a general dagger affinoid X.
(i) Duality for
$X:=\mathrm {Sp}(L[X_1, \ldots , X_d]^{\dagger })$
. As in the affine case, we can easily compute the compactly supported cohomology for the sheaf of differentials
$\Omega ^d$
. This will allow us to define the trace map.
Lemma 5.12. We have
$H^i_c(X, \Omega ^d)=0$
if
$i \neq d$
and for
$i=d$
, we have
where
$\nu =(\nu _1, \ldots , \nu _d) \in \mathbf {Z}^d$
and
$x^{\nu }=x_1^{\nu _1}x_2^{\nu _2} \dots x_d^{\nu _d}$
.
Proof. The proof is similar to the one of Lemma 5.3: if we write
$X_{\delta }:=\mathrm {Sp}(L[\delta ^{-1}X_1, \ldots , \delta ^{-1}X_d])$
, for
$\delta>1$
, then we can use the long exact sequence:
to compute
$H^i_c(X, \Omega ^d)$
(using that
$H^i(X_{\delta }, \Omega ^d)=0$
for
$i\neq 0$
).
We define the trace map for
$X=\mathrm {Sp}(L[X_1, \ldots , X_d]^{\dagger })$
as
where
$\nu =(\nu _1, \ldots , \nu _d) \in \mathbf {Z}^d$
,
$x^{\nu }=x_1^{\nu _1}x_2^{\nu _2} \dots x_d^{\nu _d}$
, and
$dx:=dx_1 \wedge \cdots \wedge dx_d$
.
Proposition 5.14. Theorem 5.11 is true for
$X=\mathrm {Sp}(L[X_1, \ldots , X_d]^{\dagger })$
.
Proof. The trace map is given by formula (5.13). The proof of the duality is the same as the one of Proposition 5.5: it is enough to prove the result for
${\mathscr {F}}={\mathscr {O}}_X$
, and in that case, the pairing can be written explicitly.
(ii) Duality for dagger affinoids. Let X be a smooth dagger affinoid of dimension d. By definition, we can find a closed immersion i of X into the Tate algebra
$Y:=\mathrm {Sp}(L[X_1, \ldots , X_N]^{\dagger })$
. All the results concerning the closed immersion i from Section 5.1.1 are still true in this case. We define the trace map for X as the composition:
Then, Theorem 5.11 follows from Proposition 5.14 the same way as Proposition 5.9 follows from Proposition 5.5.
In particular, we obtain the following proposition.
Proposition 5.15. Let X be a smooth dagger affinoid of dimension d over L, and let
${\mathscr {F}}$
be a locally free sheaf on X. Then
$H^i_c(X, {\mathscr {F}})=0$
if
$i \neq d$
.
Moreover, as in the rigid case, we have that the trace map is compatible with open immersions of dagger affinoids.
Lemma 5.16. Let X be a smooth dagger affinoid over L of dimension d. Then,
-
1. The trace map does not depend of the chosen closed immersion $X \hookrightarrow \mathrm {Sp}(L[X_1, \ldots , X_N]^{\dagger })$
. -
2. If $X \to Y$
is an open immersion of dagger smooth affinoids over L of dimension d, the composition $$\begin{align*}H^d_c(X, \Omega^d) \to H^d_c(Y, \Omega^d) \xrightarrow{\mathrm{tr}_{\mathrm{coh},Y}} L \end{align*}$$
is equal to $\mathrm {tr}_{\mathrm {coh},X}: H^d_c(X, \Omega ^d) \to L$
.
Proof. The proof can be reduced to the Stein case, that is, to Lemma 5.8.
Remark 5.17 (Topological issues).
All the terms in Theorems 5.1 and 5.11 are equipped with a natural topology and the dualities are topological. See [Reference Chiarellotto6, Theorem 4.21] for statements and discussions concerning these facts.
5.2. Coherent duality: Condensed approach
The classical coherent duality results surveyed above can be paraphrased in the condensed mathematics language.
Corollary 5.18. Let X be a smooth partially proper rigid analytic variety over L of dimension d. Then,
-
1. There are trace maps in $L_{\Box }$
and
${\mathscr {D}}(L_{\Box })$
, respectively
$\!\textit{:}$
$$ \begin{align*}\mathrm{tr} _{\mathrm{coh}}: H^d_c(X,\Omega^d_X)\to L,\quad \mathrm{tr}_{\mathrm{coh}}: \mathrm{R}\Gamma_c(X,\Omega^d)[d] \to L. \end{align*} $$
They are compatible with open immersions.
-
2. If X is Stein or proper, the pairing

is perfect, that is, it yields the quasi-isomorphisms in ${\mathscr {D}}(L_{\Box })$
(5.19) $$ \begin{align} \begin{aligned} & \Omega^j(X)\stackrel{\sim}{\to}\mathrm{R}{\mathrm{Hom}} _{L_{\Box}}(H^{d}_c(X,\Omega^{d-j}_X),L),\quad \Omega^j(X)\stackrel{\sim}{\to}{\mathrm{Hom}} _{L_{\Box}}(H^{d}_c(X,\Omega^{d-j}_X),L),\\& H^d_c(X,\Omega^j_X)\stackrel{\sim}{\to}{\mathrm{Hom}} _{L_{\Box}}(\Omega^{d-j}(X),L). \end{aligned} \end{align} $$
-
3. The pairing
![R Gamma (X, Omega sub X super j) tensor L square sub L R Gamma sub c (X, Omega sub X super d minus j) arrow R Gamma sub c (X, Omega sub X super d) arrow with tr sub coh L [-d]](data:image/gif;base64,R0lGODlhAQABAIAAAMLCwgAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==)
is perfect, that is, it yields the quasi-isomorphism in ${\mathscr {D}}(L_{\Box })$
: $$ \begin{align*} \mathrm{R}\Gamma(X,\Omega^j_X)\simeq \mathrm{R}{\mathrm{Hom}} _{L_{\Box}}(\mathrm{R}\Gamma_c(X,\Omega^{d-j}_X)[d],L). \end{align*} $$
Proof. For claim (1), assume first that X is Stein. Recall that the locally convex spaces
$H^i_c(X,\Omega ^j)$
and
$H^i(X,\Omega ^j)$
are of compact type and nuclear Fréchet (both in the classical sense), respectively. We can see them inside the category of solid L-modules. Then claim (1) follows from Proposition 5.9. For a general smooth and partially proper
$X,$
take an admissible covering
$\{U_i\}$
,
$i\in I$
, of X such that the
$U_i$
’s are Stein. We have the exact sequence:
We define the trace map
$\mathrm {tr}_{\mathrm {coh}}: H^d_c(X, \Omega _X^d) \to L$
using the above exact sequence and the fact that the construction of the coherent trace for Stein varieties is compatible with the open immersions
$U_i \cap U_j \to U_i$
(Lemma 5.8). The derived trace
$\mathrm {tr}_{\mathrm {coh}}: \mathrm {R}\Gamma _c(X,\Omega ^d) \to L$
is defined as the composition
For the last statement of claim (1), we have the following lemma.
Lemma 5.20. Let
$j:X\to Y$
be an open immersion of smooth partially proper rigid analytic varieties of dimension d over L. The coherent trace map is compatible with
$j_*$
, that is, the following diagram is commutative:

Proof. If
$X,Y$
are Stein, this follows from Lemma 5.8.
For a general partially proper Y, take an admissible covering
$\{U_i\}$
of Y by Stein varieties. Recall that the trace map
$\mathrm {tr} _{Y}: H^d_c(Y, \Omega _Y^d) \to L$
comes from the maps
$\mathrm {tr} _{U_i}: H^d_c(U_i, \Omega _{U_i}^d) \to L$
. Consider the diagram:

We want to show that the central square is commutative. Since the maps from the direct sums to
$H^d_c(X, \Omega ^d)$
and
$H^d_c(Y, \Omega ^d)$
are surjective, it suffices to show that the upper and outer trapezoids as well as the right and left triangles are commutative.
The right triangle is commutative by definition of the trace map for Y; for the upper trapezoid, it is by definition of the pushforward map. For the left triangle and the outer trapezoid, take an admissible covering
$\{U_{i,j}\}$
of each
$U_i\times _Y X$
by Stein varieties and thus reduce to
$U_i\times _Y X$
itself being Stein; then commutativity follows from the previous point.
For claim (2), we again use the cited proposition and the fact that we have
because
$H^i_c(X,\Omega ^j)$
is of compact type.
For claim (3), we cover X with Stein varieties
$\{X_i\}, i\in I$
, and consider the associated Čech hypercovering
$Y_{\scriptscriptstyle \bullet }$
of X. Then we compute in
${\mathscr {D}}(L_{\Box })$
as wanted. Here, the second quasi-isomorphism follows from the duality for Stein varieties stated in claim (2).
We have an analogous duality result in the overconvergent setting.
Corollary 5.21. Let X be a smooth dagger variety over L of dimension d. Then,
-
1. There is a trace map of solid L-modules
$$ \begin{align*}\mathrm{tr} _{\mathrm{coh}}: H^d_c(X,\Omega^d_X)\to L.\end{align*} $$
-
2. If X is an affinoid, then the pairing

is perfect, that is, it yields the quasi-isomorphisms in ${\mathscr {D}}(L_{\Box })$
: (5.22) $$ \begin{align}\begin{aligned} & H^i_c(X,\Omega^j)\stackrel{\sim}{\to}\mathrm{R}{\mathrm{Hom}} _{L_{\Box}}(H^{d-i}(X,\Omega^{d-j}_X),L),\quad H^i_c(X,\Omega^j)\stackrel{\sim}{\to}{\mathrm{Hom}} _{L_{\Box}}(H^{d-i}(X,\Omega^{d-j}_X),L),\\& H^i(X,\Omega^j)\stackrel{\sim}{\to}{\mathrm{Hom}} _{L_{\Box}}(H^{d-i}_c(X,\Omega^{d-j}_X),L).\end{aligned} \end{align} $$
-
3. If X is quasi-compact, the pairing
![R Gamma (X, Omega sub X super j) tensor product over L square R Gamma sub c (X, Omega sub X super d minus j) arrow R Gamma sub c (X, Omega sub X super d) arrow with trace sub coh L [-d]](data:image/gif;base64,R0lGODlhAQABAIAAAMLCwgAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==)
is perfect, that is, it yields the quasi-isomorphism in ${\mathscr {D}}(L_{\Box })$
: $$ \begin{align*} \mathrm{R}\Gamma_c(X,\Omega^j_X)\simeq \mathrm{R}{\mathrm{Hom}} _{L_{\Box}}(\mathrm{R}\Gamma(X,\Omega^{d-j}_X)[d],L). \end{align*} $$
Proof. The proof of (1) and (2) is the mirror image of the proof of Corollary 5.18, using Lemma 5.16, and the fact that if X is an affinoid, then the locally convex spaces
$H^i(X,\Omega ^j)$
and
$H^i_c(X,\Omega ^j)$
are of compact type and nuclear Fréchet (both in the classical sense), respectively.
For claim (3), we cover X with affinoid dagger varieties
$\{X_i\}, i\in I$
and consider the associated Čech hypercovering
$Y_{\scriptscriptstyle \bullet }$
of X. Then we compute in
${\mathscr {D}}(L_{\Box })$
as wanted. Here, the second quasi-isomorphism follows from the duality for affinoid dagger varieties stated in claim (2), and the third quasi-isomorphism follows from the fact that the limits and colimits are finite.
5.3. De Rham dualities
We state the dualities satisfied by de Rham and Hyodo–Kato cohomologies of smooth partially proper rigid analytic varieties and smooth dagger affinoids. We deduce the de Rham duality from coherent duality and the Hyodo–Kato duality is obtained from the de Rham duality using the Hyodo–Kato isomorphism.
5.3.1. Rigid analytic setting
We can now prove the duality result satisfied by the de Rham cohomology.
Theorem 5.23 (de Rham duality).
Let
$L=K,C$
and X be a smooth partially proper variety of dimension d over L. Then,
-
1. There are natural trace maps in ${\mathscr {D}}(L_{\Box })$
and
$L_{\Box }$
, respectively
$\!\textit{:}$
$$ \begin{align*}\mathrm{tr}_{\mathrm{dR} }: \, \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X)[2d]\to L,\quad \mathrm{tr}_{\mathrm{dR} }: \, H^{2d}_{\mathrm{dR} ,c}(X)\to L. \end{align*} $$
-
2. The pairing
$$ \begin{align*}\mathrm{R}\Gamma_{\mathrm{dR} }(X)\otimes^{\mathrm{L}_{\Box}}_L \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X)[2d]\to \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X)[2d]\xrightarrow{\mathrm{tr}_{\mathrm{dR} }} L \end{align*} $$
is a perfect duality, that is, we have induced quasi-isomorphisms in ${\mathscr {D}}(L_{\Box }) \textit{:}$
$$ \begin{align*} & \mathrm{R}\Gamma_{\mathrm{dR} }(X)\stackrel{\sim}{\to} \mathrm{R}{\mathrm{Hom}} _{L_{\Box}} (\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X)[2d],L). \end{align*} $$
-
3. The pairing
$$ \begin{align*}H^i_{\mathrm{dR} }(X)\otimes^{\mathrm{L}_{\Box}}_L H^{2d-i}_{\mathrm{dR} ,c}(X)\to H^{2d}_{\mathrm{dR} ,c}(X)\xrightarrow{\mathrm{tr}_{\mathrm{dR} }} L \end{align*} $$
is a perfect duality of solid L-vector spaces, that is, we have induced isomorphisms in $L_{\Box }$
$$ \begin{align*} & H^i_{\mathrm{dR} }(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{L_{\Box}} (H^{2d-i}_{\mathrm{dR} ,c}(X),L),\\ & H^i_{\mathrm{dR} ,c}(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{L_{\Box}} (H^{2d-i}_{\mathrm{dR} }(X),L). \end{align*} $$
Proof. In the case X is Stein, the trace map
$\mathrm {tr}_{\mathrm {dR} }: H^{2d}_{\mathrm {dR} ,c}(X)\to L$
can be induced by the coherent trace map
$\mathrm {tr}_{\mathrm {coh}}: H^d_c(X, \Omega _X^d) \to L$
from Corollary 5.18, noting that
$\mathrm {tr}_{\mathrm {coh}}(\partial )=0$
, where
$\partial : H^{d}_c(X, \Omega _X^{d-1}) \to H^d_c(X, \Omega _X^d)$
(see [Reference Beyer4, Lemma 2.1.4]). Its derived version
$\mathrm {tr}_{\mathrm {dR} }: \mathrm {R}\Gamma _{\mathrm {dR} ,c}(X)[2d]\to L$
is defined as the composition
In the case of general partially proper X, we reduce to the Stein case as in the proof of Corollary 5.18.
In the case X is Stein, claim (2) follows immediately from the sequence representing
$\mathrm {R}\Gamma _{\mathrm {dR} }(X)$
:
the sequence (3.13) representing
$\mathrm {R}\Gamma _{\mathrm {dR} ,c}(X)$
, and derived Serre duality (5.19). For a general partially proper X, we cover it with Stein varieties
$\{X_i\}, i\in I$
and consider the associated Čech hypercovering
$Y_{\scriptscriptstyle \bullet }$
of X. Then we compute in
${\mathscr {D}}(L_{\Box })$
as wanted. Here, the second quasi-isomorphism follows from the duality for Stein varieties.
The first isomorphism in claim (3) follows from claim (2) by taking cohomology. We use here the fact that
$\mathrm {Ext} ^j_{L_{\Box }}(H^{m}_{\mathrm {dR} ,c}(X),L)=0$
, for
$j\geq 1$
, because
$H^{m}_{\mathrm {dR} ,c}(X)$
is of compact type (in fact, a countable direct sum of finite rank vector spaces). The second isomorphism follows from the computation:
where the first isomorphism was just proven and the second one follows from reflexivity of
$H^{i}_{\mathrm {dR} ,c}(X)$
.
Lemma 5.25. Let
$j:X\to Y$
be an open immersion of smooth partially proper rigid analytic varieties of dimension d over L. The de Rham trace map is compatible with
$j_*$
, that is, the following diagram is commutative:

Proof. This follows immediately from the definition of the de Rham trace map and an analogous claim for coherent traces (see Lemma 5.20).
Corollary 5.26 (Filtered de Rham duality).
Let
$L=K,C$
and X be a smooth partially proper variety of dimension d over L. Let
$r,r^{\prime }\in \mathbf {N}, r+r^{\prime }=d$
. The pairing in
${\mathscr {D}}(L_{\Box })$
is a perfect duality, that is, we have induced quasi-isomorphisms in
${\mathscr {D}}(L_{\Box })$
Proof. Assume first that X is Stein. We compute
We wrote here
$(-)^*$
for
${\mathrm {Hom}} _{L_{\Box }}(-,L)$
and used the fact that
because the cohomology groups with compact support are of compact type. The second quasi-isomorphism follows from Corollary 5.18.
The case of X partially proper follows from the Stein case by a limit/colimit argument as in the proof of Theorem 5.23.
The duality for
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology has a different form. For
$r\geq d$
, a natural trace map in
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
can be defined by the composition
Corollary 5.27 (Filtered
${\mathbf B}^+_{\mathrm {dR} }$
-duality).
Let X be a smooth partially proper variety of dimension d over K,
$r,r^{\prime }\geq d$
and
$s=r+r^{\prime }-d$
. Then we have a natural quasi-isomorphism in
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
:
Proof. Assume first that X is Stein. This follows from the computation:
We used here the quasi-isomorphisms
which hold because we have
Here, the first quasi-isomorphism is by adjunction; the second quasi-isomorphism follows from the fact that
$H^d_c(X,\Omega ^i)$
is of compact type,
${\mathbf B}^+_{\mathrm {dR} }$
is Fréchet, and we have [Reference Rodrigues Jacinto and Rodriguez Camargo27, Theorem 3.40].
The case of X partially proper follows from the Stein case by a limit/colimit argument as in the proof of Theorem 5.23.
5.3.2. Overconvergent setting
By the same arguments as in the proof of Theorem 5.23, we deduce the Poincaré duality for de Rham cohomology.
Theorem 5.29 (de Rham duality).
Let
$L=K,C$
and X be a smooth dagger variety of dimension d over L. Then,
-
1. There are natural trace maps in ${\mathscr {D}}(L_{\Box })$
and
$L_{\Box }$
, respectively
$\!\textit{:}$
$$ \begin{align*}\mathrm{tr}_{\mathrm{dR} }: \, \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X)[2d]\to L,\quad \mathrm{tr}_{\mathrm{dR} }: \, H^{2d}_{\mathrm{dR} ,c}(X)\to L. \end{align*} $$
-
2. If X is quasi-compact, the pairing
$$ \begin{align*}\mathrm{R}\Gamma_{\mathrm{dR} }(X)\otimes^{\mathrm{L}_{\Box}}_L \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X)[2d]\to \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X)[2d]\xrightarrow{\mathrm{tr}_{\mathrm{dR} }} L \end{align*} $$
is a perfect duality, that is, we have an induced quasi-isomorphisms in ${\mathscr {D}}(L_{\Box })\textit{:}$
$$ \begin{align*} & \mathrm{R}\Gamma_{\mathrm{dR} }(X)\stackrel{\sim}{\to} \mathrm{R}{\mathrm{Hom}} _{L_{\Box}} (\mathrm{R}\Gamma_{\mathrm{dR} ,c}(X)[2d],L),\\ & \mathrm{R}\Gamma_{\mathrm{dR} ,c}(X)\stackrel{\sim}{\to} \mathrm{R}{\mathrm{Hom}} _{L} (\mathrm{R}\Gamma_{\mathrm{dR} }(X)[2d],L). \end{align*} $$
-
3. If X is quasi-compact, the pairing
$$ \begin{align*}H^i_{\mathrm{dR} }(X)\otimes^{\mathrm{L}_{\Box}}_L H^{2d-i}_{\mathrm{dR} ,c}(X)\to H^{2d}_{\mathrm{dR} ,c}(X)\xrightarrow{\mathrm{tr}_{\mathrm{dR} }} L \end{align*} $$
is a perfect duality of solid L-vector spaces, that is, we have an induced quasi-isomorphism in ${\mathscr {D}}(L_{\Box })\textit{:}$
$$ \begin{align*} & H^i_{\mathrm{dR} }(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{L_{\Box}} (H^{2d-i}_{\mathrm{dR} ,c}(X),L),\\ & H^i_{\mathrm{dR} ,c}(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{L_{\Box}} (H^{2d-i}_{\mathrm{dR} }(X),L). \end{align*} $$
Proof. In the case X is affinoid, the trace map
$\mathrm {tr}_{\mathrm {dR} }: H^{2d}_{\mathrm {dR} ,c}(X)\to L$
can be induced by the coherent trace map
$\mathrm {tr}_{\mathrm {coh}}: H^d_c(X, \Omega _X^d) \to L$
from Corollary 5.21, noting that
$\mathrm {tr}_{\mathrm {coh}}(\partial )=0$
, where
$\partial : H^{d}_c(X, \Omega _X^{d-1}) \to H^d_c(X, \Omega _X^d)$
(reduce to the Stein case and use [Reference Beyer4, Lemma 2.1.4]). Its derived version
$\mathrm {tr}_{\mathrm {dR} }: \mathrm {R}\Gamma _{\mathrm {dR} ,c}(X)[2d]\to L$
is defined as the composition
In the case of general smooth X, we reduce to the affinoid case as in the proof of Corollary 5.21.
In the case X is affinoid, the first part of claim (2) follows immediately from the sequence representing
$\mathrm {R}\Gamma _{\mathrm {dR} }(X)$
:
the analog of the sequence (3.13) representing
$\mathrm {R}\Gamma _{\mathrm {dR} ,c}(X)$
, and derived Serre duality (5.19). For a general quasi-compact X, we cover it with dagger affinoid varieties
$\{X_i\}, i\in I$
, and consider the associated Čech hypercovering
$Y_{\scriptscriptstyle \bullet }$
of X. Then we compute in
${\mathscr {D}}(L_{\Box })$
as wanted. Here, the second quasi-isomorphism follows from the duality for affinoid varieties. The second part of claim (2) follows now from the first part since
${\mathrm {R}\Gamma }_{\mathrm {dR} ,c}(X)$
is reflexive (the de Rham cohomologies
$H^i_{\mathrm {dR} ,c}(X)$
are of finite rank): we have
as wanted.
The isomorphisms in claim (3) follow from claim (2) by taking cohomology.
5.4. Hyodo–Kato duality
Using the Hyodo–Kato isomorphisms, we can deduce Poincaré duality for the Hyodo–Kato cohomology of a smooth partially proper rigid analytic variety or a smooth dagger affinoid over
$L=K,C$
from the one for de Rham cohomology.
5.4.1. Rigid analytic setting
Theorem 5.30. Let
$L=K,C$
and X be a smooth partially proper variety of dimension d over L. Set
$F_L=F, F^{\mathrm {nr}}, \breve {F}$
and
$*=-,\breve {F}$
. Then,
-
1. There is a natural trace map in the category of solid $(\varphi ,N)$
-modules over
$F_L$
$$ \begin{align*}\mathrm{tr}_{\mathrm{HK} }: \, H^{2d}_{\mathrm{HK} ,*,c}(X)\to F_L\{-d\}, \end{align*} $$
which is compatible with the de Rham trace map via the Hyodo–Kato morphism and Galois equivariant in the case $L=C$
and X is defined over K. -
2. The pairing of solid $(\varphi ,N)$
-modules over
$F_L$
$$ \begin{align*}H^i_{\mathrm{HK} ,*}(X)\otimes^{\Box}_{F_L} H^{2d-i}_{\mathrm{HK} ,*,c}(X)\to H^{2d}_{\mathrm{HK} ,*,c}(X)\xrightarrow{\mathrm{tr}_{\mathrm{HK} }} F_L\{-d\} \end{align*} $$
is a perfect duality, that is, we have induced isomorphisms of solid $(\varphi ,N)$
-modules over
$F_L$
$$ \begin{align*} & H^i_{\mathrm{HK} ,*}(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{F_{L,\Box}} (H^{2d-i}_{\mathrm{HK} ,*,c}(X),F_L\{-d\}),\\ & H^i_{\mathrm{HK} ,*,c}(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{F_{L,\Box}} (H^{2d-i}_{\mathrm{HK} ,*}(X),F_L\{-d\}). \end{align*} $$
These isomorphisms are Galois equivariant if $L=C$
and X is defined over K.
Proof. Assume first that we can define a trace map
$\mathrm {tr}_{\mathrm {HK} } : H^{2d}_{\mathrm {HK} ,*,c}(X) \to F_L\{-d\}$
such that the following diagram commutes:

Then, since the map from the bottom row is a perfect pairing, via the Hyodo–Kato isomorphisms, the top row is a perfect pairing as well and we obtain the duality for the Hyodo–Kato cohomology.
Hence, it suffices to prove claim (1). We will show that the de Rham trace map factorizes through
$F_L$
when restricted to
$H^{2d}_{\mathrm {HK} ,c}(X)$
yielding the Hyodo–Kato trace map with the required properties. We may assume that X is connected. We start with the case
$L=C$
and
$*=\breve {F}$
. Consider the following commutative diagram:

Here,
$U\subset X$
is an open ball of dimension d inside X. The bottom de Rham trace map is compatible with Frobenius as can be easily seen by passing to the affine space and using formula (5.4). The above diagram shows that the top horizontal composition factors through
$\breve {F}$
, defining the trace map
$\mathrm { tr}_{\mathrm {HK} }: H^{2d}_{\mathrm {HK} ,\breve {F},c}(X)\to \breve {F}\{-d\}$
, which is clearly compatible with the de Rham trace map and Frobenius. Moreover, the monodromy on
$H^{2d}_{\mathrm {HK} ,\breve {F},c}(X)$
is trivial (since it is so on
$H^{2d}_{\mathrm {HK} ,\breve {F},c}({\mathbb P}^d_{\breve {F}})$
), hence, the trace map
$\mathrm {tr}_{\mathrm {HK} }$
is compatible with monodromy. Same for the residual Galois action.
The same argument works for
$L=K$
(and
$F_L=F$
). For
$L=C$
and
$F_L=F^{\mathrm {nr} }$
(and
$*=-$
), we need to modify it slightly. We replace the left column in diagram (5.32) with
$F^{\mathrm {nr} }$
-cohomology and then add the following commutative diagram to the bottom:

Now, we
$F^{\mathrm {nr} }$
-linearize the bottom row. This induces an isomorphism in the left column and our claim follows.
Lemma 5.33. Let
$j:X\to Y$
be an open immersion of smooth partially proper rigid analytic varieties of dimension d over L. The Hyodo–Kato trace map is compatible with
$j_*$
, that is, the following diagram is commutative:

Proof. We will argue for
$F^{\mathrm {nr} }$
-cohomology; the argument for other
$F_L$
-cohomologies is analogous. Consider the following diagram:

We want to show that the central square commutes. For that, since the arrows from
$F^{\mathrm {nr}}$
to C are injective, it suffices to check the commutativity of the four trapezoids and the outer square. Commutativity is clear for the lower trapezoid. For the left and right trapezoids, it comes from the construction of the trace maps. For the upper one, it follows from the compatibility of the Hyodo–Kato morphism with the pushforward. It remains to show that the trace map for the de Rham cohomology is compatible with pushforward. But this is Lemma 5.25.
5.4.2. Overconvergent setting
Theorem 5.34. Let
$L=K,C$
and X be a smooth dagger variety of dimension d over L. Set
$F_L=F, F^{\mathrm {nr}}, \breve {F}$
and
$*=-,\breve {F}$
. Then,
-
1. There is a natural trace map in the category of solid $(\varphi ,N)$
-modules over
$F_L$
: $$ \begin{align*}\mathrm{tr}_{\mathrm{HK} }: \, H^{2d}_{\mathrm{HK} ,*,c}(X)\to F_L\{-d\}, \end{align*} $$
which is compatible with the de Rham trace map via the Hyodo–Kato morphism and Galois equivariant in the case $L=C$
and X is defined over K. -
2. If X is quasi-compact, the pairing of solid $(\varphi ,N)$
-modules over
$F_L$
$$ \begin{align*}H^i_{\mathrm{HK} ,*}(X)\otimes_{F_L}^{\Box} H^{2d-i}_{\mathrm{HK} ,*,c}(X)\to H^{2d}_{\mathrm{HK} ,*,c}(X)\xrightarrow{\mathrm{tr}_{\mathrm{HK} }} F_L\{-d\} \end{align*} $$
is a perfect duality of solid $F_L$
-vector spaces, that is, we have induced isomorphisms of solid
$(\varphi ,N)$
-modules over
$F_L$
: $$ \begin{align*} & H^i_{\mathrm{HK} ,*}(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{F_L,\Box} (H^{2d-i}_{\mathrm{HK} ,*,c}(X),F_L\{-d\}),\\ & H^i_{\mathrm{HK} ,*,c}(X)\stackrel{\sim}{\to} {\mathrm{Hom}} _{F_L,\Box} (H^{2d-i}_{\mathrm{HK} ,*}(X),F_L\{-d\}). \end{align*} $$
These isomorphisms are Galois equivariant if $L=C$
and X is defined over K.
Proof. For the trace map in the affinoid case, we use dagger presentations and the trace map for Stein varieties. We have an analog of Lemma 5.33 in this setting, that is, for an open immersion of smooth dagger affinoids of dimension d over K. This can be easily seen from the definition of the Hyodo–Kato trace via a reduction to Lemma 5.33. This yields, as in the proof of Corollary 5.21, the trace map for general smooth dagger varieties.
For claim (2), note first that the following diagram commutes:

That is, that the Hyodo–Kato and de Rham trace maps are compatible: which follows from the fact that the de Rham trace map can also be defined using dagger presentations and Stein trace maps. Then, since the map from the bottom row is a perfect pairing by Theorem 5.29, via the Hyodo–Kato isomorphisms, the top row is a perfect pairing as well and we obtain the duality for the Hyodo–Kato cohomology.
5.5. Examples
We will compute the de Rham and Hyodo–Kato cohomologies of the affine space and the torus and check they satisfy the previous Poincaré duality results.
5.5.1. Affine space
Let
$X={\mathbb A}_L^d$
be the affine dagger space over
$L=K,C$
. Recall that, we have
where
$F_C=F^{\mathrm {nr} }$
and
$F_K=F$
.
It follows that, by Poincaré duality, we have
The monodromy on
$ H^i_{\mathrm {HK} ,c}(X)$
is trivial and so is the action of the Galois group
$\mathrm {Gal} (\overline {K}/F^{\mathrm { nr}})$
(in the case,
$L=C$
).
We can, however, obtain this result more directly. Recall that [Reference Colmez, Dospinescu and Nizioł8, proof of Theorem 4.17], there exists a semistable weak formal scheme
${\mathscr {A}}^d$
over
${\mathscr O}_K$
such that
${\mathscr {A}}^d_K\simeq {\mathbb A}^d_K$
. Moreover, there exist closed (resp. open) subschemes
$Y_s, s\in \mathbf {N},$
(resp.
$U_s, s\in \mathbf {N}$
) of the special fiber
$Y:={\mathscr {A}}^d_0$
such that
-
1. each $Y_s$
is a finite union of irreducible components; -
2. $Y_s\subset U_s\subset Y_{s+1}$
and their union is Y; -
3. the tubes $\{\overline {U}_s:=]U_{s}[_{X}\},s\in \mathbf {N},$
form a Stein covering of
${\mathscr {A}}^d_K$
by closed discs.
We will call the covering
$\{U_s\},s\in \mathbf {N},$
a Stein covering of Y. The schemes
$U_s, Y_s$
inherit their log-structure from Y (which is canonically a log-scheme log-smooth over
$k^{0}$
). The log-schemes
$Y_s$
are not log-smooth (over
$k^0$
) but they are ideally log-smooth, that is, they have a canonical idealized log-scheme structure and are ideally log-smooth for this structure.
$\bullet $
Computation of the de Rham cohomology with compact support. We have the distinguished triangle
Since
$X\setminus \overline {U}_s$
is a complement of a closed disc, we have
The computation in (5.35) now easily follows from that fact and the distinguished triangle (5.36).
$\bullet $
Computation of the Hyodo–Kato cohomology with compact support. Similarly, we can use the distinguished triangle (everything is over F now)
where
$U^0_s$
is the naive interior of
$\overline {U}_s$
, an open disc. Since
$X\setminus \overline {U}^0_s$
has a semistable model over F, we have:
-
1. The Hyodo–Kato morphism induces an isomorphism $\iota _{\mathrm {HK} }: H^i_{\mathrm {HK} }(\partial X) \widehat {\otimes }_F K \stackrel {\sim }{\to }H^i_{\mathrm {dR} }(\partial X)$
, for all
$i \ge 0$
, and so we obtain
$ \begin {cases}H^i_{\mathrm {HK} }(\partial X)\simeq F & \text { for } i=0, \\ F & \text { for } i =2d-1, \\ 0 & \text { for } i\neq 0, 2d-1.\\ \end {cases}$
-
2. Frobenius: We have the isomorphism $H^{2d}_{\mathrm {HK} ,c}(X)\stackrel {\sim }{\to } H^{2d}_{\mathrm {HK} ,c}({\mathbb P}_K^d)$
and the Frobenius on the target group has slope d. -
3. The monodromy is trivial on $H^i_{\mathrm {HK} }(X\setminus U^0_s)$
(since the integral model has no loops) hence on
$H^i_{\mathrm {HK} }(\partial X)$
as well.
5.5.2. Torus
Let
$X:={\mathscr G}_{m,K}^d$
be a rigid analytic torus of dimension d. Recall that
$H^i_{\mathrm {dR} }({\mathscr G}_{m,K}^d)$
is a K-vector space of dimension
$\binom {d}{i}$
, generated by symbols
$c_1^{\mathrm {dR} }(z_{j_1}) \dots c_1^{\mathrm {dR} }(z_{j_i})$
for
$j_1 < j_2 < \dots < j_i$
, where
$c_1^{\mathrm {dR} }(z)= \frac {dz}{z}$
is the de Rham Chern class. Similarly,
$H^i_{\mathrm {HK} }({\mathscr G}_{m,K}^d)$
is an F-vector space of dimension
$\binom {d}{i}$
, generated by symbols
$c_1^{\mathrm {HK} }(z_{j_1}) \dots c_1^{\mathrm {HK} }(z_{j_i})$
. The Chern classes
$c_1^{\mathrm {dR} }(z)$
and
$c_1^{\mathrm {HK} }(z)$
are compatible with the Hyodo–Kato isomorphism. Moreover,
$\varphi (c_1^{\mathrm {HK} }(z))=p c_1^{\mathrm {HK} }(z)$
and
$N(c_1^{\mathrm {HK} }(z))=0$
.
Using Poincaré duality, we obtain that
$H^i_{\mathrm {dR} ,c}({\mathscr G}_{m,K}^d)$
is a K-vector space of dimension
$\binom {d}{2d-i}$
, generated by classes
$(c_1^{\mathrm {dR} }(z_{j_1}) \dots c_1^{\mathrm {dR} }(z_{j_{2d-i}}))^*$
for
$j_1 < j_2 < \dots < j_{2d-i}$
. Similarly,
$H^i_{\mathrm {HK} ,c}({\mathscr G}_{m,K}^d)$
is an F-vector space of dimension
$\binom {d}{2d-i}$
, generated by classes
$(c_1^{\mathrm {HK} }(z_{j_1}) \dots c_1^{\mathrm {HK} }(z_{j_{2d-i}}))^*$
. Monodromy acts trivially on these classes and Frobenius by multiplication by
$p^{i-d}$
.
6. Geometric syntomic cohomology with compact support
In this section, we define geometric compactly supported syntomic cohomology for both smooth rigid analytic varieties and smooth dagger varieties. In each case, the previous recipes apply and similar properties are obtained. We then show that compactly supported syntomic cohomology can be computed in terms of compactly supported (twisted) Hyodo–Kato cohomology and (quotients of) compactly supported
${\mathbf B}_{\mathrm {dR} }^+$
-cohomology. In particular, this will allow us to compare the rigid definition with the dagger one for partially proper varieties.
6.1. Rigid analytic setting
Recall (see [Reference Colmez and Nizioł14, §4.1]) that geometric syntomic cohomology is defined by
$\eta $
-étale descent from the crystalline syntomic cohomology of Fontaine–Messing
$\mathrm {R}\Gamma _{ \mathrm {syn} }({\mathscr {X}}, \mathbf {Q}_p(r)):=[F^r\mathrm {R}\Gamma _{\mathrm {cr} }({\mathscr {X}}) \xrightarrow {p^r- \varphi } \mathrm {R}\Gamma _{\mathrm {cr} }({\mathscr {X}})]$
. By regarding the crystalline sheaves as condensed abelian groups, we can define the sheaf
${\mathscr {A}}_{ \mathrm {syn} }(r)$
on
$\mathrm {Sm}_{C,\mathrm {\acute {e}t} }$
as a sheaf with values in
${\mathscr D}({\mathbf {Q}_{p,\Box }})$
and set
$\mathrm {R}\Gamma _{ \mathrm {syn} }(X,\mathbf {Q}_p(r)):= \mathrm {R}\Gamma _{\mathrm {\acute {e}t} }(X, {\mathscr {A}}_{ \mathrm {syn} }(r))$
for
$X \in \mathrm {Sm}_{\mathrm {\acute {e}t} , C}$
. Following the usual process, we define the compactly supported cohomology
$\mathrm {R}\Gamma _{ \mathrm {syn} ,c}(X,\mathbf {Q}_p(r)) \in {\mathscr D}(\mathbf {Q}_{p,\Box })$
of a smooth variety X over C. It satisfies all the properties from Section 2.1.
Recall that we have the following theorem.
Theorem 6.1 [Reference Colmez and Nizioł15, Corollary 5.5].
Let
$X \in \mathrm {Sm}_{C}$
and
$r \ge 0$
. There is a natural quasi-isomorphism in
${\mathscr D}({\mathbf {Q}_{p,\Box }})$
:
where
![[R Gamma H K (X) tensor L square F n r B plus s t] N=0, phi=p^r is defined as a commutative diagram of R Gamma H K (X) tensor L square F n r B plus s t with horizontal maps (1-phi/p^r) and (1-phi/p^r-1) and vertical maps N.](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu253.png?pub-status=live)
Proof. The proof is given in [Reference Colmez and Nizioł15, §5.1]. Let us recall how it goes to see that it still works in the condensed setting: We work locally. The quasi-isomorphism for the local statement is induced by the quasi-isomorphisms
$\iota _{\mathrm { BK}}^1$
and
$\iota _{\mathrm {BK}}^2$
given by the following commutative diagram:
![Commutative diagram of cohomology groups. Top-left [R Gamma H K (X) tensor B st super +] N=0 maps right to R Gamma d R (X / B d R super +) / F super r and down to [R Gamma cr (X) tensor B st super +] N=0. Bottom row shows R Gamma cr (X) to R Gamma cr (X) / F super r.](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu254.png?pub-status=live)
where the quasi-isomorphism
$\varepsilon ^{\mathrm {HK} }_{\mathrm {st} }$
is the quasi-isomorphism from the proof of Proposition 3.18 and
$\iota _{\mathrm {BK},r}$
is the one from (3.4).
We will prove below in Proposition 6.4 that we have an analogous result for the compactly supported cohomology. Let us first define and prove some properties satisfied by the twisted Hyodo–Kato cohomology and the quotients of
${\mathbf B}_{\mathrm {dR} }^+$
-cohomology. We take
$X\in \mathrm {Sm}_C$
.
(i) Twisted Hyodo–Kato cohomology. We set
Lemma 6.2. There is a natural quasi-isomorphism in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
:
where
$\mathrm {HK} (\partial X,r):= \mathrm {colim} _{Z\in \Phi } \mathrm {HK} (X \setminus Z,r)$
.
Proof. We need to show that we have a quasi-isomorphism
But this follows from the fact that taking the colimit commutes with
.
(ii)
${\mathbf B}^+_{\mathrm {dR} }$
-cohomology and its quotients. Recall that we set
Arguing as in the proof of Lemma 6.2, we get the following lemma.
Lemma 6.3. There is a natural quasi-isomorphism in
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
:
where
$\mathrm {DR} (\partial X,r):= \mathrm {colim} _{Z\in \Phi } \mathrm {DR} (X \setminus Z,r)$
.
(iii) Comparison with syntomic cohomology. As in the classical case, we can compute compactly supported syntomic cohomology in terms of compactly supported Hyodo–Kato and
${\mathbf B}_{\mathrm {dR} }^+$
- cohomologies.
Proposition 6.4. There is a natural quasi-isomorphism in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
:
such that for all quasi-compact open
$Z \subset X$
, the following diagram commutes in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
:

Proof. We deduce from Lemmas 6.2 and 6.3 that we have a commutative diagram in which rows are distinguished triangles:

The second column is a distinguished triangle by Theorem 6.1, so it suffices to check that the third column is a distinguished triangle as well. But for
$Z \subset X$
a quasi-compact open, we have
and we deduce the result by taking the colimit over all
$Z\in \Phi $
.
6.2. Overconvergent setting
The definition of the compactly supported syntomic cohomology of a dagger variety is the same as the one of the pro-étale cohomology: we first give a local definition using presentation of dagger affinoids, and then (co)sheafify it.
6.2.1. Definition
If X is a dagger affinoid over C with a presentation
$\{X_h\}_{h \in \mathbf {N}}$
, we define in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
For a general smooth dagger variety X over C, using the natural equivalence
we define the cosheaf
${\mathscr {A}}_{ \mathrm {syn} ,c}(r)$
on
$X_{\mathrm {an}}$
as the cosheaf associated with the precosheaf defined by
$U\mapsto \mathrm {R}\Gamma ^{\natural }_{ \mathrm {syn} ,c}(U,\mathbf {Q}_p(r)), U\in \mathrm {SmAff}^{\dagger }_{L}$
,
$U\to X$
an admissible open. We set
Lemma 6.5. Let X be in
$\mathrm {Sm}_C^{\dagger }$
.
-
1. (Local–global compatibility) If X is a dagger affinoid, then the natural map in ${\mathscr {D}}(\mathbf {Q}_{p,\Box })\textit{:}$
$$ \begin{align*}\mathrm{R}\Gamma_{ \mathrm{syn} ,c}(X,\mathbf{Q}_p(r))\to \mathrm{R}\Gamma^{\natural}_{ \mathrm{syn} ,c}(X,\mathbf{Q}_p(r))\end{align*} $$
is a quasi-isomorphism.
-
2. (Passing to completion) If X is partially proper, then there is natural quasi-isomorphism in ${\mathscr {D}}(\mathbf {Q}_{p,\Box })\textit{:}$
$$ \begin{align*}\mathrm{R}\Gamma_{ \mathrm{syn} ,c}({X},\mathbf{Q}_p(r))\stackrel{\sim}{\to} \mathrm{R}\Gamma_{ \mathrm{syn} ,c}(\widehat{X},\mathbf{Q}_p(r)). \end{align*} $$
Proof. For the first claim, it suffices to show that for any open covering
$X=X_1\cup X_2$
by dagger affinoids, we have the Mayer–Vietoris distinguished triangle
Choosing a presentation
$\{ X_h \}$
of X, an
$h\in \mathbf {N}$
, and using excision, we can write this triangle as
That this triangle is distinguished can be seen by passing to twisted Hyodo–Kato and
${\mathbf B}^+_{\mathrm {dR} }$
-cohomologies.
Let us now prove claim (2). If X is Stein, take
$\{ U_n \}$
an increasing covering of X by admissible dagger affinoids. We have a commutative diagram:

where the second row is the distinguished triangle (6.7). (We note that there is no circular reasoning here: Remark 6.6 uses only the first claim of this lemma.) The second and third vertical arrows are quasi-isomorphisms by the usual comparison results between overconvergent cohomologies and their rigid analytic analogs (see [Reference Colmez and Nizioł14]). We obtain that the first vertical map (defined by the diagram) is a quasi-isomorphism as well.
Since a general partially proper variety X is locally Stein, we can conclude by analytic codescent.
Remark 6.6. As for pro-étale cohomology, if X is smooth and Stein and
$\{U_n\}$
an increasing quasi-compact covering of X with
$U_n \Subset U_{n+1}$
, we define the cohomology of the boundary of X as
The same proof as for (4.6) shows that we have a distinguished triangle in
${\mathscr D}({\mathbf {Q}_{p,\Box }})$
:
6.2.2. Passage to the Bloch–Kato version
As in the rigid analytic, we can express compactly supported syntomic cohomology in terms of compactly supported de Rham and Hyodo–Kato cohomologies. We define the twisted Hyodo–Kato cohomology and the quotients of the
${\mathbf B}_{\mathrm {dR}}^+$
-cohomology as in the rigid case:
![H K sub c (X, r) is defined as [R Gamma sub H K, c (X) tensor product over F super nr with B sub st super +] super N=0, phi=p super r. D R sub c (X, r) is defined as R Gamma sub d R, c (X / B sub d R super +) / F super r.](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu273.png?pub-status=live)
The first one lives in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
, and the second one in
${\mathscr {D}}({\mathbf B}^+_{\mathrm {dR} ,\Box })$
.
Proposition 6.8. For all
$i\ge 0$
and
$r\ge 0$
, we have in
${\mathbf {Q}_{p,\Box }}$
Proof. The result for the compactly supported cohomology follows from the result in the classical case working with dagger affinoids and using the long exact sequence defining the cohomology with compact support. So it suffices to prove the result for
$\mathrm {HK} (X,r)$
. An analogous result in the classical setting was proved in [Reference Colmez, Dospinescu and Nizioł8, Example 3.16] (and extended in [Reference Colmez and Nizioł15, Proposition 4.24]). The proof in the condensed setting is similar, the main difference is that
${\mathbf B}_{\mathrm {st} }^+$
is already flat for the solid tensor product
.
We first prove that we have
Since
$\mathrm {{\mathbf B}^+_{\mathrm {st} }} $
is flat over F, we have a natural quasi-isomorphism in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
This yields the distinguished triangle:
and, by taking the cohomology, we get

We repeat the same computation to obtain the isomorphism (6.9) for all i.
We now assume that
$X:= {\mathscr {X}}_C$
for
${\mathscr {X}}$
in the category of basic semistable formal models
${\mathscr {M}}_C^{\dagger , \mathrm {ss,b}}$
. The proposition in that case follows from the isomorphism (6.9) and from the two exact sequences:

for M a finite
$(\varphi ,N)$
-module (the first one is proved by recurrence on the integer m such that
$N^m=0$
, and the second one is proved in the same way as in [Reference Colmez and Nizioł13, Remark 2.30]).
In the general case, take
${\mathscr {U}}_{\bullet }$
an étale hypercovering of X from
${\mathscr {M}}_C^{\dagger , \mathrm {ss,b}}$
. By the previous paragraph, the proposition is true for each
${\mathscr {U}}_{i,C}$
. We then use the two following spectral sequences to conclude:

(to get the second one, we use the flatness of
$\mathrm {{\mathbf B}^+_{\mathrm {st} }} $
and the fact that the differentials are
$\mathrm {{\mathbf B}^+_{\mathrm {st} }} $
-linear).
As in the rigid case, we can write syntomic cohomology in terms of Hyodo–Kato and de Rham cohomologies.
Proposition 6.10. Let X be a smooth dagger variety over C. There is a natural quasi-isomorphism in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })\textit{:}$
Proof. It suffices to show the result for the
$\natural $
-cohomologies. Let X be an affinoid dagger space and
$\{ X_h \}$
be a presentation of X. Consider the following commutative diagram:

where we set
![H K sub c natural (X, r) defined as [R Gamma sub H K, c natural (X) tensor product over F super nr B sub st super +] with N=0, phi=p^r. D R sub c natural (X, r) defined as R Gamma sub d R, c natural (X / B sub d R super +) / F^r.](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu282.png?pub-status=live)
The first row in the above diagram is a distinguished triangle by definition, and the second and third ones are clearly distinguished triangles. The second and third column are distinguished triangles by Proposition 6.1. It follows that the first column is a distinguished triangle as well.
We will need the following lemma.
Lemma 6.11. Let
$j:X \hookrightarrow Y$
be an open immersion of smooth dagger varieties over C, then the following diagram commutes:

Similarly, for the Hyodo–Kato map,
$\iota _{\mathrm {HK} }: \mathrm {R}\Gamma _{\mathrm {HK} ,c}(-)\to \mathrm {R}\Gamma _{\mathrm {dR} ,c}(-)$
.
Proof. We can work locally. Let
$X \hookrightarrow Y$
be an open immersion of dagger affinoids and take
$\{ X_h \}$
and
$\{ Y_h \}$
presentations of X and
$Y,$
respectively, such that we have open immersions
$X_h \hookrightarrow Y_h$
. Recall that the maps
$j_*: \mathrm {R}\Gamma ^{\natural }_{ \mathrm {syn} ,c}(X,r) \to \mathrm {R}\Gamma ^{\natural }_{ \mathrm {syn} ,c}(Y,r)$
and
$\mathrm {HK} _c(X,r) \to \mathrm {HK} _c(Y,r)$
are induced by the compositions:
The commutativity of the diagram in the lemma is now clear. The argument for the Hyodo–Kato map is analogous.
6.3. Period morphism
We show that we have a period isomorphism comparing syntomic cohomologies with pro-étale cohomologies with compact support from the previous section. This will allow us to compute explicitly p-adic pro-étale cohomologies in the next section of the article.
6.3.1. Rigid analytic period morphism
Recall that, for all
$X \in \mathrm {Sm}_C$
, we have a period morphism in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })\!:$
that is, a quasi-isomorphism after truncation
$\tau _{\leq r}$
(see [Reference Colmez and Nizioł14, Corollary 7.3]). By functoriality, it induces a period morphism in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })\textit{:}$
Theorem 6.13. For X in
$\mathrm {Sm}_C$
and
$r\ge 0$
, the map
$\alpha _{r,c}$
is a quasi-isomorphism in
${\mathscr D}({\mathbf {Q}_{p,\Box }}):$
Proof. This follows from the map of distinguished triangles:

The second and third vertical maps are quasi-isomorphisms (after truncation
$\tau _{\le r}$
). Note here that truncation commutes with colimits. Hence, the first vertical map is a quasi-isomorphism after truncation
$\tau _{\leq r}$
as well.
6.3.2. Overconvergent period morphism
Let X be a dagger affinoid over C and let
$\{X_h\}$
be a presentation of X. We have compatible period maps in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })\!:$
that are quasi-isomorphisms after truncation
$\tau _{\le r}$
. They induce a local period morphism for the compactly supported cohomology:
and this map is a quasi-isomorphism in
${\mathscr {D}}(\mathbf {Q}_{p.\Box })$
after taking the truncation.
We can know globalize the above construction and we obtain the following theorem.
Theorem 6.14. For X in
$\mathrm {Sm}^{\dagger }_C$
and
$r\ge 0$
, there is a quasi-isomorphism in
${\mathscr D}(\mathbf {Q}_{p,\Box })$
:
6.3.3. Geometrization of the period morphism
We define
$\mathrm {TVS}$
(for topological vector spaces) as the
$\infty $
derived category of
$\underline {\mathbf {Q}}_p$
-modules in presheaves of solid abelian groups on the category
$\mathrm {Perf}_C$
of perfectoid spaces over C. The usual Fontaine’s period rings
have canonical structures of
$\mathrm {TVS}$
s that we will denote by
${\mathbb {B}}_{\mathrm {dR} }^+,{\mathbb {B}}_{\mathrm {cr} }^+, {\mathbb {B}}_{\mathrm {st} }^+, {\mathbb {B}}_{\mathrm {dR} },{\mathbb {B}}_{\mathrm {cr} }, {\mathbb {B}}_{\mathrm {st} }$
, respectively. As in [Reference Colmez and Nizioł15, §7], we will see that we can endow the cohomologies defined in the previous sections with a
$\mathrm {TVS}$
-structure and that the period morphism can be lifted to this category.
(i) Rigid analytic setting. If X is a smooth rigid analytic variety over C, we write
${\mathbb {H}}^i_{\mathrm {pro\acute {e}t} }(X, \mathbf {Q}_p), i\in \mathbf {N}$
, (resp.
${\mathbb {R}}_{\mathrm {pro\acute {e}t} }(X, \mathbf {Q}_p)$
) for the functor on
$\mathrm {Perf}_C$
defined as
where
$X_{\Lambda }$
is the base change
$X\times _C \Lambda $
. These define objects in
$\mathrm {TVS}$
.
On the other hand, the syntomic cohomology can be geometrized by tensoring
$\mathrm {R}\Gamma _{\mathrm {HK} }(X) \otimes ^{\mathrm {L}_{\Box }}_{\breve {F}}{\mathbf B}_{\mathrm {st} }^+$
with
$- \otimes _{{\mathbf B}_{\mathrm {st} }^+}^{\mathrm {L}_{\Box }} {\mathbb {B}}_{\mathrm {st} }^+$
and
$F^r\mathrm {R}\Gamma _{\mathrm {dR} }(X/ {\mathbf B}_{\mathrm {dR} }^+)$
with
$- \otimes _{{\mathbf B}_{\mathrm {dR} }^+}^{\mathrm {L}_{\Box }} {\mathbb {B}}_{\mathrm {dR} }^+$
to obtain
${\mathbb {R}}_{\mathrm {syn}}(X, \mathbf {Q}_p(r)), r \ge 0$
.
Recall that the period morphism can be lifted to
$\mathrm {TVS}$
.
Proposition 6.15 (Colmez and Nizioł [Reference Colmez and Nizioł15, Theorem 7.3]).
Let
$X\in \mathrm {Sm}_C$
and
$r \ge 0$
. The functorial period map in
${\mathscr {D}}(\mathbf {Q}_{p, \Box })$
lifts to a functorial map of TVSs (with values in
${\mathscr {D}}(\mathbf {Q}_{p, \Box } )$
):
which is a quasi-isomorphism after truncation
$\tau _{\le r}$
.
Similarly, for X a smooth rigid analytic variety over C, we endow
$\mathrm {R}\Gamma _{\mathrm {pro\acute {e}t} ,c}(X, \mathbf {Q}_p(r))$
and
$\mathrm {R}\Gamma _{\mathrm {syn},c}(X, \mathbf {Q}_p(r))$
with a
$\mathrm {TVS}$
-structure by setting
There are canonical quasi-isomorphisms:
where
${\mathbb {R}}_{*}(\partial X, \mathbf {Q}_p(r)):= \mathrm {colim} _{Z \in \Phi } {\mathbb {R}}_*(X \setminus Z, \mathbf {Q}_p(r))$
, for
$* \in \{ \mathrm {pro\acute {e}t} , \mathrm {syn}\}$
. It follows easily from Proposition 6.15 that the period morphism for compactly supported cohomology can be lifted to the category
$\mathrm {TVS}$
.
Proposition 6.16. There exists a natural map of
$\mathrm {TVS}$
(with values in
${\mathscr {D}}(\mathbf {Q}_{p, \Box } )$
):
lifting the morphism (6.12). Moreover, it is a quasi-isomorphism after truncation
$\tau _{\le r}$
.
(ii) The overconvergent setting. We have a similar picture for dagger varieties. Let X be a dagger affinoid over C, let
$\{X_h\}_{h\in \mathbf {N}}$
be a presentation, and let
$\widehat {X}$
be the associated rigid analytic variety. We define the
$\mathrm { TVS}$
:
We then extend this definition to any smooth dagger variety X over C, by étale cosheafification and get
$\mathrm {TVS}$
s:
${\mathbb {R}}_{*,c}(X, \mathbf {Q}_p(r))$
.
Now, for smooth dagger affinoids X over C, using the rigid analytic period morphism
$\mathbb {\alpha }_{r,c}$
from (6.17), we get a period morphism of
$\mathrm {TVS}$
s
which globalizes to a period morphism that lifts the period morphism
$\alpha ^{\dagger }_{r,c}$
from Theorem 6.14. It is a quasi-isomorphism after truncation
$\tau _{\le r}$
. To sum up, we have the following proposition.
Proposition 6.18. There exists a natural map of
$\mathrm {TVS}$
(with values in
${\mathscr {D}}(\mathbf {Q}_{p, \Box } )$
):
lifting the morphism (6.14). It is a quasi-isomorphism after truncation
$\tau _{\le r}$
.
7. Computations
We present here computations of geometric compactly supported p-adic pro-étale cohomology of some Stein varieties using the period morphisms from Section 2 and the duality results from Section 5. In particular, our computations show the existence of trace maps that will be used to prove Poincaré duality for geometric p-adic pro-étale cohomology in [Reference Colmez, Gilles and Nizioł11].
7.1. Affine space
Let us first consider the case of the affine rigid space of dimension d over K. Using the distinguished triangle from Proposition 6.4, we can compute its compactly supported syntomic cohomology.
Proposition 7.1. Let
$X:={\mathbb A}_K^d$
,
$d\geq 1$
, be the rigid analytic affine space of dimension d over K.
-
1. Let $r\geq 0$
. We have the following isomorphisms in
$\mathbf {Q}_{p,\Box }$
: $$ \begin{align*} & H^{i}_{ \mathrm{syn} ,c}(X_C,\mathbf{Q}_p(r)) =0, \quad i<d, i>2d;\\ & H^{i}_{ \mathrm{syn} ,c}(X_C,\mathbf{Q}_p(r)) \simeq (H_c^d(X, \Omega^{i-d-1})/\mathrm{Ker}~d)\otimes_K^{\Box}\mathrm{gr}_F^{r-i+d}{\mathbf B}^+_{\mathrm{dR} }, \quad d \le i \le 2d-1. \end{align*} $$
-
2. If $0\leq r<d$
, then
$H_{ \mathrm {syn} ,c}^{2d}(X_C, \mathbf {Q}_p(r)) =0$
. If
$r\geq d$
, then we have an exact sequence in
$\mathbf {Q}_{p,\Box }$
: $$ \begin{align*}0 \to (H_c^d(X_C, \Omega^{d-1})/ \mathrm{Ker}~d) (r-d) \to H_{ \mathrm{syn} ,c}^{2d}(X_C, \mathbf{Q}_p(r)) \to \mathbf{Q}_p(r-d) \to 0. \end{align*} $$
Proof. Clearly,
$H^{i}_{ \mathrm {syn} ,c}(X_C,\mathbf {Q}_p(r)) =0$
, for
$i<d$
.
Let
$0\leq i\leq d-1$
. Since
$ H^{i+d}_{\mathrm {HK} ,c}(X_C,r)= H^{i+d-1}_{\mathrm {HK} ,c}(X_C,r)=0, $
we obtain from Lemma 3.16 that
For the same reasons,
$H^{i+d}_{ \mathrm {syn} ,c}(X_C,\mathbf {Q}_p(r)) =0$
if
$i> d+1$
.
For
$i=d$
, by Section 5.5.1, we have
And, by Lemma 3.16, we have
Hence, we get the exact sequence:
If
$r<d$
, this yields
If
$r\geq d$
, we have a fundamental exact sequence of p-adic Hodge theory:
Hence,
$H_{ \mathrm {syn} ,c}^{2d+1}(X_C, \mathbf {Q}_p(r))=0$
and we get the exact sequence
as wanted.
The following corollary follows immediately from Proposition 7.1 and the period isomorphism from Theorem 6.13.
Corollary 7.2. Let
$X:={\mathbb A}_K^d$
,
$d\geq 1$
, be the rigid analytic affine space of dimension d over K.
-
1. We have the following isomorphisms in $\mathbf {Q}_{p,\Box }$
: $$ \begin{align*} & H^{i}_{\mathrm{pro\acute{e}t} ,c}(X_C,\mathbf{Q}_p) =0, \quad i<d, i>2d;\\ & H^{i}_{\mathrm{pro\acute{e}t} ,c}(X_C,\mathbf{Q}_p(i-d)) \simeq H_c^d(X_C, \Omega^{i-d-1})/\mathrm{Ker}~d \text{ if } d\le i \le 2d-1. \end{align*} $$
-
2. We have an exact sequence in $\mathbf {Q}_{p,\Box }$
: $$ \begin{align*}0 \to H_c^d(X_C, \Omega^{d-1})/ \mathrm{Ker}~d\to H_{\mathrm{pro\acute{e}t} ,c}^{2d}(X_C, \mathbf{Q}_p(d)) \to \mathbf{Q}_p \to 0. \end{align*} $$
Example 7.3 (Dimension 1).
For
$d=1$
and
$r\geq 0$
, Proposition 7.1 yields:
-
1. $H^0_{ \mathrm {syn} ,c}({\mathbb A}_C^1, \mathbf {Q}_p(r))=0$
,
$H^i_{ \mathrm {syn} ,c}({\mathbb A}_C^1, \mathbf {Q}_p(r))=0$
, for
$i\geq 3$
. -
2. $H^1_{ \mathrm {syn} ,c}({\mathbb A}_C^1, \mathbf {Q}_p(r))=0.$
-
3. $H^2_{ \mathrm {syn} ,c}({\mathbb A}_C^1, \mathbf {Q}_p)=0$
. -
4. For $r\geq 1$
, an exact sequence of solid
$\mathbf {Q}_p$
-modules: $$\begin{align*}0 \to H^1_c({\mathbb A}_C^1,{\mathscr O}) (r-1) \to H^2_{ \mathrm{syn} ,c}({\mathbb A}_C^1, \mathbf{Q}_p(r)) \to \mathbf{Q}_p(r-1) \to 0. \end{align*}$$
In the last point, we have used the fact that the map
$H^1_c({\mathbb A}_C^1,{\mathscr O})\to H^1_c({\mathbb A}_C^1,\Omega ^1)$
is injective (since
$H^1_{\mathrm {dR} ,c}({\mathbb A}_C^1)=0$
).
This yields:
-
1. $H^i_{\mathrm {pro\acute {e}t} ,c}({\mathbb A}_C^1, \mathbf {Q}_p)=0$
, for
$i\neq 2$
; -
2. an exact sequence of solid $\mathbf {Q}_p$
-modules $$\begin{align*}0 \to H^1_c({\mathbb A}_C^1,{\mathscr O}) \to H^2_{\mathrm{pro\acute{e}t} ,c}({\mathbb A}_C^1, \mathbf{Q}_p(1)) \to \mathbf{Q}_p\to 0. \end{align*}$$
7.2. Stein curves
We now compute the compactly supported p-adic cohomology of Stein curves. Let X be a smooth Stein variety over K of dimension
$d= 1$
. For
$i\geq 0$
, we have an exact sequence
We have in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
:
![Three lines of mathematical isomorphisms. Line 1: R Gamma d R, c (X) tensor B d R plus is isomorphic to (H c 1 (X, O X) tensor B d R plus arrow H c 1 (X, Omega X 1) tensor B d R plus) [-1]. Lines 2 and 3 show filtered and D R variants.](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu313.png?pub-status=live)
In particular,
$H^j\mathrm {DR}_c(X_C,i)=0$
, for
$j\neq 1,2.$
We also have (see Proposition 6.8)
By the Poincaré duality,
where the first dual is the
$F^{\mathrm {nr}}$
-dual and the second one—the C-dual; the twist
$\{n\}$
on de Rham cohomology shifts the filtration by n, that is,
$F^i_{\mathrm {new}}=F^{i+n}_{\mathrm {old}}$
. It follows that
This implies that
$H^i_{\mathrm {pro\acute {e}t} ,c}(X_C,\mathbf {Q}_p)=0$
for
$i\neq 1,2,3$
.
$\bullet $
The group
$H^1_{\mathrm {pro\acute {e}t} ,c}(X_C,\mathbf {Q}_p)$
. We have the exact sequence of solid
$\mathbf {Q}_p$
-modules
By (7.5), this yields the exact sequence
From Lemma 3.14, we obtain an isomorphism
$ H^1\mathrm {DR} _c(X_C,1) \simeq H^1_c(X_C, {\mathscr O}) $
and from Proposition 6.8,
. But the map
factorizes as
where the second morphism is injective. So the kernel of the second arrow in (7.6) is isomorphic to the kernel of the first arrow in (7.7). This is equal to
(see [Reference Colmez, Dospinescu and Nizioł8, Lemma 3.39] or Lemma 8.1 below) and so we get
$\bullet $
The group
$H^2_{\mathrm {pro\acute {e}t} ,c}(X_C,\mathbf {Q}_p)$
. The long exact sequence above gives the exact sequence:
Using (7.4) and (7.5), we get the exact sequence
Recall now that we have a fundamental exact sequence
Using it, we get the exact sequence
where the first term is isomorphic to
.
Remark 7.10. By duality, the slopes of the Frobenius on
$H^1_{\mathrm {HK} ,c}(X_C)$
are between
$0$
and
$1$
. If we assume that they are
$0$
, then, we can show that we have an exact sequence
To see that first note that, from Lemma 3.14, we get an exact sequence
and since the slopes of the Frobenius on
$H^1_{\mathrm {HK} ,c}(X_C)$
are
$\le 1$
, we have the following exact sequence (see [Reference Colmez, Dospinescu and Nizioł8, Lemma 3.39] or Lemma 8.1 below):
Combining (7.12) and (7.13), we see that the cokernel of the first map in (7.9) is isomorphic to the cokernel of the map
which in turn factorizes as
But, if the slopes of the Frobenius are zero, then the first map is surjective (see Lemma 8.1 below) so the cokernel we want is isomorphic to the cokernel of the map on the right, which gives the exact sequence (7.11).
$\bullet $
The group
$H^3_{\mathrm {pro\acute {e}t} ,c}(X_C,\mathbf {Q}_p)$
. We claim that
$H^3_{\mathrm {pro\acute {e}t} ,c}(X_C,\mathbf {Q}_p)=0$
. Indeed, we have the exact sequence
The last term on the right is zero for dimension reasons. By Lemma 3.14, the first map is isomorphic to the Hyodo–Kato map
Since
$N=0$
and
$\varphi =p$
on
$H^{2}_{\mathrm {HK,c}}(X_C)$
and we have compatible isomorphisms
$H^{2}_{\mathrm {HK,c}}(X_C)\simeq F^{\mathrm {nr} }$
,
$H^{2}_{\mathrm {dR} ,c}(X)\simeq K$
, this map can be written as
which is surjective, as wanted.
7.3. Trace maps
The purpose of this section is to define trace maps for the p-adic pro-étale cohomology of smooth partially proper varieties and dagger affinoids of dimension d over K. To do that, we use the period isomorphism to express
$H^{2d}_{\mathrm {pro\acute {e}t} ,c}(X, \mathbf {Q}_p(r))$
in terms of Hyodo–Kato and de Rham cohomologies and then we use the trace morphisms from Section 5. We then show that these trace maps satisfy various compatibilities.
7.3.1. Partially proper varieties and dagger affinoids
Let X be a smooth partially proper variety or a smooth dagger affinoid over K. Assume that it is of dimension
$d\geq 1$
and geometrically irreducible. We have an exact sequence of solid
$\mathbf {Q}_p$
-modules
Since
$N=0$
and
$\varphi =p^d$
on
$H^{2d}_{\mathrm {HK,c}}(X_C)$
, we get an exact sequence
Via the compatible trace maps
this yields an exact sequence
Hence, a natural trace map of solid
$\mathbf {Q}_p$
-modules
This map is surjective. We will denote in the same way the derived trace map in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
obtained as the composition
![tr sub proét, X sub C colon R Gamma sub proét, c (X sub C, Q sub p (2d)) [2d] left arrow with tilde tau sub less than or equal to 2d R Gamma sub proét, c (X sub C, Q sub p (2d)) [2d] arrow H super 2d sub proét, c (X sub C, Q sub p (2d)) arrow Q sub p (d).](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20261022103731237-0775:S002776302610138X:S002776302610138X_eqnu330.png?pub-status=live)
Remark 7.15 (Proper varieties).
Assume that X is proper in the above. Then we see that the first map in the exact sequence (7.14) is injective and it follows that the trace map is an isomorphism
7.3.2. Properties of trace maps
The trace morphisms defined above satisfy the following compatibilities.
Lemma 7.16. The trace map
$\mathrm {tr}_{\mathrm {pro\acute {e}t} ,X_C}$
is compatible with
-
1. the corresponding Hyodo–Kato and de Rham trace maps, that is, the following diagrams commute in $\mathbf {Q}_{p,\Box }$
: 
-
2. open immersions $j:X\hookrightarrow Y$
, where
$X, Y$
are partially proper varieties or dagger affinoids over K.
Proof. The compatibility (1) is clear from the construction. For compatibility (2), we first assume that X and Y are partially proper and consider the following diagram of solid
$\mathbf {Q}_p$
-modules:

We want to show that the upper square is commutative. We know that the upper trapezoid is commutative. The right and left triangles are commutative by claim (1). Since the arrows from
$\mathbf {Q}_p(d)$
to
${\mathbf B}_{\mathrm {cr} }^{+, \varphi =p^d}$
are injective, it suffices then to prove the commutativity of the outer trapezoid. or that the geometric Hyodo–Kato trace is compatible with the open immersion
$X\hookrightarrow Y$
. But this was shown in Lemma 5.33.
The proof is similar when X and Y are both dagger affinoids, using the proof of Theorem 5.34.
7.3.3. Comparison with Berkovich’s trace map
This section will not be used in the rest of the article. Let X be a smooth partially proper rigid analytic variety of dimension d over K. Recall (see Lemma 2.3) that we have a canonical map in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })\!:$
where
$\mathrm {R}\Gamma _{\mathrm {\acute {e}t} ,c}(X_C,\mathbf {Q}_p)=(\lim _n\mathrm {R}\Gamma _{\mathrm {\acute {e}t} ,c}(X_C,\mathbf {Z}/p^n))\otimes ^{\Box }_{\mathbf {Z}_p}\mathbf {Q}_p$
. We also have (compatible with n) Berkovich’s trace maps (see [Reference Berkovich3, §7.2]):
that induce a trace map in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
:
We will call the composition
the pro-étale Berkovich trace map.
Proposition 7.17. The two trace maps in
${\mathscr {D}}(\mathbf {Q}_{p,\Box })$
are equal.
Proof. By the spectral sequence (2.31), we have a surjection in
$\mathbf {Q}_{p,\Box }{:}$
where the index set
$ \{U_i\}$
runs over a covering family of open discs. Hence, we may assume that X is an open disc. Then, since both trace maps are compatible with open immersions of partially proper rigid analytic varieties (by Lemma 7.16 and [Reference Zavyalov32, Theorem 5.3.3], respectively), we may assume that X is the projective space:
$X={\mathbb P}^{d,\mathrm {an}}_C$
.
Now, we can drop the compact support everywhere and then pass to the algebraic category. It suffices thus to compare the trace maps
where the first trace map is the algebraic analog of
$\mathrm {tr} _{\mathrm {pro\acute {e}t} , X_C}$
(so defined via comparison theorems) and the second trace map is the classical algebraic étale trace map. That this passage works this way follows from GAGA-type theorems in [Reference Shao29] and the compatibility of the algebraic and analytic étale trace maps. Now, the equality of the two trace maps in (7.18) follows from the known fact that the classical comparison theorems are compatible with trace maps (this reduces to a comparison of Chern class maps).
8. Stein varieties
We construct here a conditional version of a fundamental diagram for geometric compactly supported p-adic pro-étale cohomology of Stein varieties and apply it to determine such cohomology of tori and Drinfeld’s spaces. The proofs are similar to the ones of [Reference Colmez, Dospinescu and Nizioł8], but more complicated due to the shift by d that appears in the term coming from the compactly supported de Rham cohomology.
8.1. Fundamental diagram
Let X be a smooth dagger Stein variety of dimension d over K. The purpose of this section is to study the compactly supported p-adic pro-étale cohomology of
$X_C$
. To do that, we need to extend some of the results of [Reference Colmez, Dospinescu and Nizioł8] and, in particular, their Lemma 3.39.
Lemma 8.1. Let j, k, and l be in
$\mathbf {N}$
such that
$k \le j$
. There is an exact sequence in
$\mathbf {Q}_{p,\Box }{:}$
Moreover, the right arrow is surjective if the slopes of the Frobenius on
$H^l_{\mathrm {HK} ,c}(X_C)$
are
$\le j-k$
.
Proof. The case
$k=0$
was proved in [Reference Colmez, Dospinescu and Nizioł8, Lemma 3.39]. For
$k \neq 0$
, it is clear that the multiplication by
$t^{k+1}$
is injective, it remains to show the exactness in the middle. To do that, as in [Reference Colmez, Dospinescu and Nizioł8, Lemma 3.39], it suffices to show that for all
$\delta $
,
$(F^{k+1}\mathrm {{\mathbf B}^+_{\mathrm cr}} )^{\varphi =p^{j+1- \delta }}=(t^{k+1} \mathrm {{\mathbf B}^+_{\mathrm cr}} )^{\varphi =p^{j+1- \delta }}$
, where we set
$F^k \mathrm {{\mathbf B}^+_{\mathrm cr}} =\mathrm {{\mathbf B}^+_{\mathrm cr}} \cap F^k {\mathbf B}_{\mathrm {dR} }^+$
. Clearly,
$(t^{k+1}\mathrm {{\mathbf B}^+_{\mathrm cr}} )^{\varphi =p^{j+1- \delta }}\subset (F^{k+1} \mathrm {{\mathbf B}^+_{\mathrm cr}} )^{\varphi =p^{j+1- \delta }}.$
We prove the other inclusion by induction. For
$k=0$
, we have
Let
$k \ge 0$
. By induction, it suffices to prove that for all
$\delta $
,
$(F^{k+1}\mathrm {{\mathbf B}^+_{\mathrm cr}} )^{\varphi =p^{j+1-\delta }}\subset (t F^k\mathrm {{\mathbf B}^+_{\mathrm cr}} )^{\varphi =p^{j+1-\delta }}$
. Let y be in
$(F^{k+1}\mathrm {{\mathbf B}^+_{\mathrm cr}} )^{\varphi =p^{j+1-\delta }}$
, then
$y=t^{k+1}y_0$
with
$y_0$
in
${\mathbf B}_{\mathrm {dR} }^+$
and we have
We obtain that
$t^ky_0$
is in
$\mathrm {{\mathbf B}^+_{\mathrm cr}} \cap F^k {\mathbf B}_{\mathrm {dR} }^+=F^k \mathrm {{\mathbf B}^+_{\mathrm cr}} $
, which concludes the proof of the first statement of the lemma.
Let us prove that if the slopes of the Frobenius on
$H^l_{\mathrm {HK} ,c}(X_C)$
are
$\le j-k$
, then
$\pi ^{l,j+1}_{k+1}$
is surjective. We show by induction that for all
$1 \le m \le k+1$
, the map
is surjective. For
$m=1$
, the result follows from [Reference Colmez, Dospinescu and Nizioł8, Lemma 3.39] (the slopes of the Frobenius are less or equal to
$ j-k$
so they are less or equal to j). Assume that
$\pi ^{l,j+1}_{m-1}$
is surjective. The surjectivity of
$\pi ^{l,j+1}_{m}$
will follow from the commutative diagram:

The first row is exact, the vertical arrow
$\pi ^{l,j+1}_{m-1}$
is surjective by the inductive assumption, and the left vertical arrow is surjective since the morphism
is surjective (the slopes of the Frobenius are less or equal to
$j-k$
so as long as m is less than
$k+1$
, the slopes are less or equal to
$j-m+1$
). We deduce that
$\pi ^{l,j+1}_{m}$
is surjective, as wanted.
Remark 8.2. Since the slopes of Frobenius on
$H^l_{\mathrm {HK} }(X_C)$
are between
$0$
and l, by duality, the slopes of the Frobenius on
$H^l_{\mathrm {HK} ,c}(X_C)$
are between
$d-(2d-l)=l-d$
and
$d-0=d$
.
Proposition 8.3. Assume that the maps
$\pi ^{r-1,r}_{d}$
and
$\pi ^{r-1,r-d}_1$
are surjective. Then there is an exact sequence in
$\mathbf {Q}_{p,\Box }$
:
Proof. Consider the following commutative diagram:

where
$\mathrm {HK} ^*_c(X_C):=H^*_{\mathrm {HK} ,c}(X_C)$
,
$H^d_c(\Omega ^{*}):=H^d_c(X_C, \Omega ^*)$
and the maps
$\gamma _{r-1}$
,
$\gamma _r$
are obtained by factorization. The rows are exact sequences by Lemmas 3.14 and 8.1 (and by assumption on
$\pi _d^{r-1,r}$
for the bottom row). The column in the middle is an exact sequence as well. We deduce that we have an exact sequence:
and it remains to compute
$\mathrm {Ker} (\gamma _r)$
and
$\mathrm {coker} (\gamma _{r-1})$
.
(
$\bullet $
) Kernel of
$\gamma _r$
. The map
$\gamma _r$
factorizes as
with
$\gamma _{r}^{(2)}$
injective. Then,
as wanted.
(
$\bullet $
) Cokernel of
$\gamma _{r-1}$
. As above, the map
$\gamma _{r-1}$
factorizes as
with
$\gamma _{r-1}^{(2)}$
injective. The hypothesis that
$\pi _1^{r-1,r-d}$
is surjective implies that
$\gamma _{r-1}^{(1)}$
is surjective as well. So,
and we obtain the exact sequence from the proposition.
Using the previous lemma, we obtain a bicartesian diagram analogous to the one of [Reference Colmez, Dospinescu and Nizioł8, Example 3.35] to compute the compactly supported syntomic cohomology of Stein varieties.
Theorem 8.4. Assume that the maps
$\pi ^{r-1,r}_{d}$
and
$\pi ^{r-1,r-d}_1$
are surjective. Then, there is a map of exact sequences in
$\mathbf {Q}_{p,\Box }$
:

Proof. The first row is exact by the previous proposition and the exactness of the second one is implied by the definition of the de Rham cohomology
$H^{i+d}_{\mathrm {dR} ,c}(X_C)= H^i(H^d_c(X_C, \Omega ^{\bullet }))$
. The map
$\alpha $
is given by the composition:
and
$\beta $
is the morphism:
We then show that the diagram is commutative using the same argument as in the classical case [Reference Colmez, Dospinescu and Nizioł8, Example 3.35].
Corollary 8.5. Let X be a smooth Stein variety of dimension d over K and
$r\ge 0$
. Assume that the maps
$\pi ^{r-1,r}_{d}$
and
$\pi ^{r-1,r-d}_1$
are surjective. Then there is a bicartesian diagram in
$\mathbf {Q}_{p,\Box }$
:

Corollary 8.6. Let X be a smooth Stein variety of dimension d over K, and let
$r\geq 0$
. The hypotheses of Theorem 8.4 are satisfied if and only if
$H_{\mathrm {HK} }^{2d-r+1}(X_C)$
is pure of Frobenius slope
$2d-r+1$
. Or, equivalently, if and only if
$H_{\mathrm {HK} ,c}^{r-1}(X_C)$
is pure of Frobenius slope
$r-d-1$
.
Proof. In fact, the second map of Theorem 8.4 already characterizes the purity and then the first map is automatically surjective. Here is our argument. Set
$ M:=H^{r-1}_{\mathrm {HK} ,c}(X_C), a:=r-d. $
Lemma 8.7. The map
$\pi _1^{r-1,r-d}$
is surjective if and only if the slopes of M are at most
$a-1$
.
Proof. If
$r\leq d$
, then
$M=0$
and the assertion is immediate. We may thus assume that
$r\geq d+1$
.
Lemma 8.1 states that
$\pi _1^{r-1,r-d}$
is surjective when the slopes of M are at most
$a-1.$
But the converse follows from the same Banach–Colmez dimension calculation used in the proof of the original [Reference Colmez, Dospinescu and Nizioł8, Lemma 3.39]. Indeed, using Banach–Colmez–Mittag-Leffler, we may assume that M is of finite rank over
$F^{\mathrm {nr} }$
. After trivializing N, consider
We have an injection
$ Q_a\hookrightarrow M\otimes _{F^{\mathrm {nr} }}^{\Box } C. $
The Banach–Colmez dimension computation gives
where the
$\lambda _i$
’s are the Frobenius slopes of M, repeated with multiplicity. The target
$M\otimes _{F^{\mathrm {nr}}}^{\Box } C$
of
$\pi _1^{r-1,r-d}$
has dimension
$(\mathrm {dim}_{F^{\mathrm {nr} }} \,M,0).$
Formula (8.8) equals this dimension precisely when every
$\lambda _i\leq a-1$
. If some slope lies in
$(a-1,a],$
a positive height appears; if some slope is
$>a$
, its contribution is missing altogether. Giving us what we wanted.
Now, Hyodo–Kato duality and the usual slope bound give
$\mathrm {Slopes}(M)\subset [r-d-1,d]=[a-1,d].$
Therefore, Lemma 8.7 says that
$\pi _1^{r-1,r-d}$
is surjective if and only if M is pure of slope
$a-1=r-d-1.$
Finally, under this purity condition, the other map
$\pi _d^{r-1,r}$
is automatically surjective by Lemma 8.1, since the compact slope
$r-d-1 $
is certainly at most
$r-d.$
8.2. Examples
We will now use Theorem 8.4 to compute the compactly supported geometric p-adic pro-étale cohomology of tori and Drinfeld spaces.
8.2.1. Torus
We will use the previous formula to compute the compactly supported pro-étale cohomology of the torus
$X:={\mathscr G}_{m,K}^d$
. For
$0\leq r\le d-1$
, we have
$H^r_{\mathrm {pro\acute {e}t} ,c}(X_C,\mathbf {Q}_p)=0$
since
$H^i_{\mathrm {dR} ,c}(X_C)=0,$
for
$i\leq d-1$
. Assume thus that
$d \le r \le 2d$
.
Now, from Section 5.5.2, we know that the monodromy on
$H^{r-1}_{\mathrm {HK} ,c}(X_C)$
is trivial and the Frobenius slope is
$r-1-d$
. By Corollary 8.6 and Theorem 8.4, we obtain a map of exact sequences in
$\mathbf {Q}_{p,\Box }$
:

For comparison, we have
$H_{\mathrm {\acute {e}t} ,c}^{r}(X_C, \mathbf {Q}_p(r-d))\simeq H_{\mathrm {\acute {e}t} ,c}^{r}(X^{\mathrm {alg}}_C, \mathbf {Q}_p(r-d))\simeq \wedge ^{2d-r} \mathbf {Q}_p^d$
.
Remark 8.10. Recall that, for the usual cohomology, we have an exact sequence in
$\mathbf {Q}_{p,\Box }$
(see [Reference Colmez, Dospinescu and Nizioł8, §4.3.2]),
We claim that, for any smooth Stein variety X over C, we have an isomorphism in
$C_{\Box }{:}$
This observation together with diagram (8.9) was a starting point of the study of dualities for p-adic pro-étale cohomology in [Reference Colmez, Gilles and Nizioł11]. To prove the isomorphism (8.11), let
$r^{\prime }=d-r$
and consider the exact sequence
Dualizing, we get the exact sequence (note that all the terms in (8.12) are nuclear Fréchet and use [Reference Rodrigues Jacinto and Rodriguez Camargo27, Theorem 3.40])
Using Poincaré duality from Theorem 5.23, we obtain the exact sequence (where
$r^{\prime }=d-r$
)
Hence, an isomorphism (8.11), as wanted.
8.2.2. Drinfeld’s space
We now treat the case of the Drinfeld space
$X:=\mathbb {H}_K^d$
. Recall that we have natural isomorphisms of solid K- and
$F^{\mathrm {nr}}(\varphi ,N)$
-modules, respectively (see [Reference Colmez, Dospinescu and Nizioł8, Lemma 5.11]):
where
$\mathrm {Sp}_i(-)$
is the generalized locally constant Steinberg representation (see [Reference Colmez, Dospinescu and Nizioł8, §5.2.1]). We note that the monodromy on
$ H^i_{\mathrm {HK} }(\mathbb {H}_C^d)$
is trivial. For
$i>d$
,
$H^{i}_{\mathrm {dR} }(\mathbb {H}_K^d)=0$
. Hence, we have natural isomorphisms of solid K- and
$F^{\mathrm {nr}}(\varphi ,N)$
-modules, respectively:
In particular, the monodromy on
$ H^i_{\mathrm {HK} ,c}(\mathbb {H}_C^d)$
is trivial and the Frobenius slope is
$i-d$
. For
$i<d$
, we have
$H^{i}_{\mathrm {dR} ,c}(\mathbb {H}_K^d)=0$
, hence
$H^{i}_{\mathrm {pro\acute {e}t} ,c}(\mathbb {H}_C^d, \mathbf {Q}_p)=0$
.
Assume thus that
$r\geq d$
. From Corollary 8.6 and Theorem 8.4, we obtain the map of exact sequences in
$\mathbf {Q}_{p,\Box }$
:

For comparison, we have an isomorphism (see [Reference Colmez, Dospinescu, Hauseux and Nizioł9, Theorem 1.2])
where
$\mathrm {Sp}^{\mathrm {cont}}_i(-)$
is the generalized continuous Steinberg representations (see [Reference Colmez, Dospinescu and Nizioł8, §5.2.1]). Hence, we should have a commutative diagram (we did not check compatibilities)

Acknowledgements
This article is a continuation of a joint project of W.N. with Pierre Colmez to whom we are very grateful for the inspiration and endless discussions. We would like to thank Gabriel Dospinescu, Zhenghui Li, Xinyu Shao, and Bogdan Zavyalov for helpful comments and discussions concerning the content of this article and its earlier drafts. S.G. would like to thank the MPIM of Bonn and the IAS of Princeton for their support and hospitality during the academic years 2022–2023 and 2023–2024, when parts of this article were written. W.N. would like to thank the Banach Center in Warsaw for its support and hospitality during the Spring semester of 2022, when parts of this article were written.
Funding statement
W.N.’s research was supported in part by the grant NR-19-CE40-0015-02 COLOSS, the NSF (Grant No. DMS-1440140), and the Simons Collaboration on Perfection in Algebra, Geometry, and Topology. P.A. and W.N. were supported by the project KAPIBARA funded by the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (Grant Agreement No. 802787). S.G.’s research was partially supported by the National Science Foundation under Grant No. DMS-1926686 and by the ERC under the European Union’s Horizon 2020 Research and Innovation Programme (Grant Agreement No. 804176).




