Derived induction theory for the K-theory of modular group algebras

TL;DR

This paper establishes an induction theorem for higher algebraic K-groups of group algebras over finite fields, simplifying calculations for certain finite groups by leveraging categorical Green functors and modular representation theory.

Contribution

It introduces a spectral Green functor framework for K-theory of group algebras and provides explicit calculations for p-isolated groups with small Sylow p-subgroups.

Findings

Reduction of K-theory calculations to p-subgroups for p-isolated groups

Construction of a spectral Green functor structure on K-theory

Explicit new calculations of K-groups for specific finite groups

Abstract

We prove an induction theorem for the higher algebraic K-groups of group algebras $kG$ of finite groups $G$ over characteristic $p$ finite fields $k$. For a certain class of finite groups, which we call $p$-isolated, this reduces calculations to calculations for their $p$-subgroups. We do so by showing that the stable module categories of $kH$ as $H$ ranges over subgroups of $G$ assemble into a categorical Green functor, which results in a spectral Green functor structure on K-theory. By general induction theory, this reduces proving a spectrum-level induction statement to proving an induction statement on $\pi_0$ Green functors, which we accomplish using modular representation theory. For $p$-isolated groups with Sylow $p$-subgroups of order $p$, we produce explicit new calculations of K-groups.