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We demonstrate that companionships and conjunctions in double $\infty$-categories -- and more generally, in double Segal spaces -- extend to functors out of the free-living companionship and conjunction respectively. Specifically, we prove…

Category Theory · Mathematics 2025-04-09 Jaco Ruit

Let $G$ be a compact connected Lie group. We show that the category $\mathbf{Loc}_{\infty}(BG)$ of $\infty$-local systems on the classifying space of $G$, can be described infinitesimally as the category…

Algebraic Topology · Mathematics 2021-05-04 Camilo Arias Abad , Santiago Pineda Montoya , Alexander Quintero Velez

Through a study of torsion functors of local cohomology modules we improve some non-finiteness results on the top non-zero local cohomology modules with respect to an ideal.

Commutative Algebra · Mathematics 2010-10-15 Mohammad T. Dibaei , Alireza Vahidi

We show that contracting self-similar groups satisfy the Farrell-Jones conjectures as soon as their universal contracting cover is non-positively curved. This applies in particular to bounded self-similar groups. We define, along the way, a…

K-Theory and Homology · Mathematics 2015-01-29 Laurent Bartholdi

We give a necessary and sufficient condition in terms of group cohomology for two indecomposable module categories over a group-theoretical fusion category ${\mathcal C}$ to be equivalent. This concludes the classification of such module…

Quantum Algebra · Mathematics 2017-06-20 Sonia Natale

One way to understand the mod p homotopy theory of classifying spaces of finite groups is to compute their BZ/p-cellularization. In the easiest cases this is a classifying space of a finite group (always a finite p-group). If not, we show…

Algebraic Topology · Mathematics 2007-05-23 R. J. Flores , J. Scherer

We show that, in a highest weight category with duality, the endomorphism algebra of a tilting object is naturally a cellular algebra. Our proof generalizes a recent construction of Andersen, Stroppel, and Tubbenhauer. This result raises…

Representation Theory · Mathematics 2026-02-11 Gwyn Bellamy , Ulrich Thiel

It is a well known result in the covering groups that a subgroup $G$ of the fundamental group at the identity of a semi-locally simply connected topological group determines a covering morphism of topological groups with characteristic…

Algebraic Topology · Mathematics 2016-01-27 Osman Mucuk , Tunçar Şahan

This paper studies Emerton's Jacquet module functor for locally analytic representations of p-adic reductive groups. When P is a parabolic subgroup whose Levi factor M is not commutative, we show that passing to an isotypical subspace for…

Number Theory · Mathematics 2011-08-30 Richard Hill , David Loeffler

We investigate the similarities and differences between the module of symmetric tensors TS^n_A(M) and the module of divided powers \Gamma^n_A(M). There is a canonical map \Gamma^n_A(M) \to TS^n_A(M) which is an isomorphism in many important…

Commutative Algebra · Mathematics 2008-03-24 Christian Lundkvist

Let $G$ be a group acting on a category $\mathcal{C}$. We give a definition for a functor $F\colon \mathcal{C} \to \mathcal{C}'$ to be a $G$-covering and three constructions of the orbit category $\mathcal{C}/G$, which generalizes the…

Representation Theory · Mathematics 2011-02-22 Hideto Asashiba

The principal aim of this note is to give an elementary proof of the fact that any two fiber functors of a Tannakian category are locally isomorphic. This builds on an idea of Deligne concerning scalar extensions of Tannakian categories and…

Algebraic Geometry · Mathematics 2018-05-10 Daniel Schäppi

This paper is a commutative algebra introduction to the homological theory of quasi-coherent sheaves and contraherent cosheaves over quasi-compact semi-separated schemes. Antilocality is an alternative way in which global properties are…

Commutative Algebra · Mathematics 2024-02-26 Leonid Positselski

We give necessary and sufficient conditions for the functor that forgets the $(C, \gamma)$-coaction to be separable. This leads to a generalized notion of integrals. Finally, the applications of our results are considered.

Rings and Algebras · Mathematics 2015-01-13 Shuangjian Guo , Xiaohui Zhang

We prove that the forgetful functor from groupoids to pregroupoids has a left adjoint, with the front adjunction injective. Thus we get an enveloping groupoid for any pregroupoid. We prove that the category of torsors is equivalent to that…

Category Theory · Mathematics 2007-05-23 Anders Kock

We exhibit a bridge between the theory of cellular categories, used in algebraic topology and homological algebra, and the model-theoretic notion of stable independence. Roughly speaking, we show that the combinatorial cellular categories…

Category Theory · Mathematics 2022-04-05 Michael Lieberman , Jiří Rosický , Sebastien Vasey

In this article, we are concerned with the Langlands functoriality conjecture. Cogdell, Kim, Piatetski-Shapiro and Shahidi proved functioriality conjecture in the case of a globally generic cuspidal automorphic representation for the split…

Number Theory · Mathematics 2022-01-11 Héctor del Castillo

We give a general construction of categorical idempotents which recovers the categorified Jones-Wenzl projectors, categorified Young symmetrizers, and other constructions as special cases. The construction is intimately tied to cell theory…

Algebraic Topology · Mathematics 2020-02-25 Matthew Hogancamp

We establish that a category of fibrant objects (in the sense of Brown) admits a Dwyer-Kan homotopical calculus of right fractions. This is done using a homotopical calculus of cocycles, which is an auxiliary structure that can be defined…

Category Theory · Mathematics 2015-09-29 Zhen Lin Low

A simplicial set is said to be non-singular if the representing map of each non-degenerate simplex is degreewise injective. The inclusion into the category of simplicial sets, of the full subcategory whose objects are the non-singular…

Algebraic Topology · Mathematics 2020-01-17 Vegard Fjellbo