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Sato–Tate distributions and Galois endomorphism modules in genus 2

Published online by Cambridge University Press:  25 July 2012

Francesc Fité
Affiliation:
Department of Mathematics, Universität Bielefeld, Postfach 100131, D-33501 Bielefeld, Germany (email: francesc.fite@gmail.com)
Kiran S. Kedlaya
Affiliation:
Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA (email: kedlaya@mit.edu, kedlaya@ucsd.edu)
Víctor Rotger
Affiliation:
Departament Matemàtica Aplicada II, Universitat Politècnica de Catalunya, Campus Nord, Edifici Omega, Despatx 413, Jordi Girona, 1-3, 08034 Barcelona, Spain (email: victor.rotger@upc.edu)
Andrew V. Sutherland
Affiliation:
Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA (email: drew@math.mit.edu)
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Abstract

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For an abelian surface A over a number field k, we study the limiting distribution of the normalized Euler factors of the L-function of A. This distribution is expected to correspond to taking characteristic polynomials of a uniform random matrix in some closed subgroup of USp(4); this Sato–Tate group may be obtained from the Galois action on any Tate module of A. We show that the Sato–Tate group is limited to a particular list of 55 groups up to conjugacy. We then classify A according to the Galois module structure on the ℝ-algebra generated by endomorphisms of $A_{{\overline {\mathbb Q}}}$ (the Galois type), and establish a matching with the classification of Sato–Tate groups; this shows that there are at most 52 groups up to conjugacy which occur as Sato–Tate groups for suitable A and k, of which 34 can occur for k=ℚ. Finally, we present examples of Jacobians of hyperelliptic curves exhibiting each Galois type (over ℚ whenever possible), and observe numerical agreement with the expected Sato–Tate distribution by comparing moment statistics.

Information

Type
Research Article
Copyright
Copyright © Foundation Compositio Mathematica 2012