The spectrum of global representations for families of bounded rank and VI-modules

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Hauptverfasser: Barrero, Miguel, Barthel, Tobias, Pol, Luca, Strickland, Neil, Williamson, Jordan
Format: Preprint
Veröffentlicht: 2025
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author Barrero, Miguel
Barthel, Tobias
Pol, Luca
Strickland, Neil
Williamson, Jordan
author_facet Barrero, Miguel
Barthel, Tobias
Pol, Luca
Strickland, Neil
Williamson, Jordan
contents A global representation is a compatible collection of representations of the outer automorphism groups of the finite groups belonging to a family $\mathscr{U}$. These arise in classical representation theory, in the study of representation stability, as well as in global homotopy theory. In this paper we begin a systematic study of the derived category $\mathsf{D}(\mathscr{U};k)$ of global representations over fields $k$ of characteristic zero, from the point-of-view of tensor-triangular geometry. We calculate its Balmer spectrum for various infinite families of finite groups including elementary abelian $p$-groups, cyclic groups, and finite abelian $p$-groups of bounded rank. We then deduce that the Balmer spectrum associated to the family of finite abelian $p$-groups has infinite Krull dimension and infinite Cantor--Bendixson rank, illustrating the complex phenomena we encounter. As a concrete application, we provide a complete tt-theoretic classification of finitely generated derived VI-modules. Our proofs rely on subtle information about the growth behaviour of global representations studied in a companion paper, as well as novel methods from non-rigid tt-geometry.
format Preprint
id arxiv_https___arxiv_org_abs_2506_21525
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The spectrum of global representations for families of bounded rank and VI-modules
Barrero, Miguel
Barthel, Tobias
Pol, Luca
Strickland, Neil
Williamson, Jordan
Representation Theory
Algebraic Topology
Category Theory
A global representation is a compatible collection of representations of the outer automorphism groups of the finite groups belonging to a family $\mathscr{U}$. These arise in classical representation theory, in the study of representation stability, as well as in global homotopy theory. In this paper we begin a systematic study of the derived category $\mathsf{D}(\mathscr{U};k)$ of global representations over fields $k$ of characteristic zero, from the point-of-view of tensor-triangular geometry. We calculate its Balmer spectrum for various infinite families of finite groups including elementary abelian $p$-groups, cyclic groups, and finite abelian $p$-groups of bounded rank. We then deduce that the Balmer spectrum associated to the family of finite abelian $p$-groups has infinite Krull dimension and infinite Cantor--Bendixson rank, illustrating the complex phenomena we encounter. As a concrete application, we provide a complete tt-theoretic classification of finitely generated derived VI-modules. Our proofs rely on subtle information about the growth behaviour of global representations studied in a companion paper, as well as novel methods from non-rigid tt-geometry.
title The spectrum of global representations for families of bounded rank and VI-modules
topic Representation Theory
Algebraic Topology
Category Theory
url https://arxiv.org/abs/2506.21525