Representations of categories of G-maps

TL;DR

This paper investigates the algebraic and homological properties of wreath product categories related to finite sets, establishing noetherianity and stability results, and introduces quasi-ordered languages to analyze Hilbert series.

Contribution

It proves noetherian properties for wreath product categories with polycyclic-by-finite groups and introduces quasi-ordered languages for rationality results in finite group cases.

Findings

Noetherianity for injective wreath product categories with certain groups.

Homological stability results for wreath products.

Rationality of Hilbert series using quasi-ordered languages.

Abstract

We study representations of wreath product analogues of categories of finite sets. This includes the category of finite sets and injections (studied by Church, Ellenberg, and Farb) and the opposite of the category of finite sets and surjections (studied by the authors in previous work). We prove noetherian properties for the injective version when the group in question is polycyclic-by-finite and use it to deduce general twisted homological stability results for such wreath products and indicate some applications to representation stability. We introduce a new class of formal languages (quasi-ordered languages) and use them to deduce strong rationality properties of Hilbert series of representations for the surjective version when the group is finite.