Invariants de classes : le cas semi-stable

Abstract

We define here an analogue, for a semi-stable group scheme whose generic fiber is an abelian variety, of M. J. Taylor's class-invariant homomorphism (defined for abelian schemes), and we give a geometric description of it. Then we extend a result of Taylor, Srivastav, Agboola and Pappas concerning the kernel of this homomorphism in the case of a semi-stable elliptic curve.

16 pages, LaTeX. Minor changes. Accepted for publication in Compositio Mathematica