Non-abelian Anderson A-modules: Comparison isomorphisms and Galois representations

TL;DR

This paper studies non-abelian Anderson A-modules, focusing on their motives, comparison isomorphisms, and Galois representations, providing new insights even for abelian cases and linking Galois images to motivic groups.

Contribution

It introduces new structural results for non-abelian Anderson A-modules, generalizes Anderson's uniformizability criterion, and relates special functions to Galois representations and motivic Galois groups.

Findings

Established structure of motives for non-abelian Anderson A-modules.

Generalized Anderson's uniformizability criterion to broader cases.

Connected special functions to Galois representations and motivic Galois groups.

Abstract

In this manuscript, we consider non-abelian Anderson $A$-modules $E$ (of generic characteristic). The main results are on the structure of their motives, and on comparison isomorphisms between their cohomological realizations. In the center of these comparison isomorphisms, there is the space of special functions $\mathfrak{sf}(E)$ as defined by Gazda and the author in arXiv:1903.07302. We also provide a generalization of Anderson's result on the equivalence of uniformizability of the Anderson module and rigid analytic triviality of its associated motive. We contribute results that are new even in the case of abelian Anderson modules. For every non-zero prime ideal $\mathfrak{p}$ of $A$, the relation of the space of special functions to the $\mathfrak{p}$-adic Tate module provides a way to obtain $\mathfrak{p}^{n+1}$-torsion as special values of hyperderivatives of these special functions. Using this result for uniformizable Anderson modules, we are able to describe the $\mathfrak{p}$-adic Galois representation via a rigid analytic trivialization, and hence give a direct link between the image of the $\mathfrak{p}$-adic Galois representation and the motivic Galois group. This generalizes results of various authors.