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Relation between two twisted inverse image pseudofunctors in duality theory

Published online by Cambridge University Press:  19 November 2014

Srikanth B. Iyengar
Affiliation:
Department of Mathematics, University of Nebraska, Lincoln, NE 68588, USA email s.b.iyengar@unl.edu
Joseph Lipman
Affiliation:
Department of Mathematics, Purdue University, West Lafayette, IN 47907, USA email jlipman@purdue.edu
Amnon Neeman
Affiliation:
Centre for Mathematics and its Applications, Mathematical Sciences Institute Australian National University, Canberra, ACT 0200, Australia email Amnon.Neeman@anu.edu.au
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Abstract

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Grothendieck duality theory assigns to essentially finite-type maps $f$ of noetherian schemes a pseudofunctor $f^{\times }$ right-adjoint to $\mathsf{R}f_{\ast }$, and a pseudofunctor $f^{!}$ agreeing with $f^{\times }$ when $f$ is proper, but equal to the usual inverse image $f^{\ast }$ when $f$ is étale. We define and study a canonical map from the first pseudofunctor to the second. This map behaves well with respect to flat base change, and is taken to an isomorphism by ‘compactly supported’ versions of standard derived functors. Concrete realizations are described, for instance for maps of affine schemes. Applications include proofs of reduction theorems for Hochschild homology and cohomology, and of a remarkable formula for the fundamental class of a flat map of affine schemes.

Information

Type
Research Article
Copyright
© The Author(s) 2014