A Categorical Decomposition of $\mathbb C^{\times}$-fibered $p$-biset Functors

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Main Authors: Coşkun, Olcay, Muslumov, Ruslan
Format: Preprint
Published: 2025
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author Coşkun, Olcay
Muslumov, Ruslan
author_facet Coşkun, Olcay
Muslumov, Ruslan
contents We generalize Bouc's construction of orthogonal idempotents in the double Burnside algebra to the setting of the double $\mathbb{C}^\times$-fibered Burnside algebra. This yields a structural decomposition of the evaluations of $\mathbb{C}^\times$-fibered biset functors on finite groups. We then construct a complete set of orthogonal idempotents in the category of $\mathbb{C}^\times$-fibered $p$-biset functors, leading to a categorical decomposition of this category into subcategories indexed by isomorphism classes of atoric $p$-groups. Furthermore, we introduce the notion of vertices for indecomposable functors and establish that the Ext-groups between simple functors with distinct vertices vanish. As an application, we describe a set containing composition factors of the monomial Burnside functor, thereby providing new insights into its structure. Additionally, we develop a technique for analyzing fibered biset functors via their underlying biset structures.
format Preprint
id arxiv_https___arxiv_org_abs_2505_15163
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Categorical Decomposition of $\mathbb C^{\times}$-fibered $p$-biset Functors
Coşkun, Olcay
Muslumov, Ruslan
Representation Theory
K-Theory and Homology
We generalize Bouc's construction of orthogonal idempotents in the double Burnside algebra to the setting of the double $\mathbb{C}^\times$-fibered Burnside algebra. This yields a structural decomposition of the evaluations of $\mathbb{C}^\times$-fibered biset functors on finite groups. We then construct a complete set of orthogonal idempotents in the category of $\mathbb{C}^\times$-fibered $p$-biset functors, leading to a categorical decomposition of this category into subcategories indexed by isomorphism classes of atoric $p$-groups. Furthermore, we introduce the notion of vertices for indecomposable functors and establish that the Ext-groups between simple functors with distinct vertices vanish. As an application, we describe a set containing composition factors of the monomial Burnside functor, thereby providing new insights into its structure. Additionally, we develop a technique for analyzing fibered biset functors via their underlying biset structures.
title A Categorical Decomposition of $\mathbb C^{\times}$-fibered $p$-biset Functors
topic Representation Theory
K-Theory and Homology
url https://arxiv.org/abs/2505.15163