Formal groups, supersingular abelian varieties and tame ramification

Abstract

Let us consider an abelian variety defined over Qℓ with good supersingular reduction. In this paper we give explicit conditions that ensure that the action of the wild inertia group on the ℓ-torsion points of the variety is trivial. Furthermore we give a family of curves of genus 2 such that their Jacobian surfaces have good supersingular reduction and satisfy these conditions. We address this question by means of a detailed study of the formal group law attached to abelian varieties.