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We introduce the notion of $\pi$-cosupport as a new tool for the stable module category of a finite group scheme. In the case of a finite group, we use this to give a new proof of the classification of tensor ideal localising subcategories.…

Representation Theory · Mathematics 2017-01-09 Dave Benson , Srikanth B. Iyengar , Henning Krause , Julia Pevtsova

In this paper, we define indexed type theories which are related to indexed ($\infty$-)categories in the same way as (homotopy) type theories are related to ($\infty$-)categories. We define several standard constructions for such theories…

Category Theory · Mathematics 2023-06-22 Valery Isaev

In this paper we prove that various quasi-categories whose objects are $\infty$-categories in a very general sense are complete: admitting limits indexed by all simplicial sets. This result and others of a similar flavor follow from a…

Category Theory · Mathematics 2019-10-04 Emily Riehl , Dominic Verity

We extend Bourke and Garner's idempotent adjunction between monads and pretheories to the framework of $\infty$-categories and we use this to prove many classical results about monads in the $\infty$-categorical framework. Amongst other…

Category Theory · Mathematics 2021-06-17 Simon Henry , Nicholas J. Meadows

In this paper we introduce the models for $(\infty, n)$-categories which have been developed to date, as well as the comparisons between them that are known and conjectured. We review the role of $(\infty, n)$-categories in the proof of the…

Algebraic Topology · Mathematics 2012-12-20 Julia E. Bergner

Although $S_\infty$ (the group of all permutations of $\mathbb{N}$) is size continuum, both it and its closed subgroups can be presented as the set of paths through a countable tree. The subgroups of $S_\infty$ that can be presented this…

Logic · Mathematics 2025-08-08 Jason Block

Colimits are a fundamental construction in category theory. They provide a way to construct new objects by gluing together existing objects that are related in some way. We introduce a complementary notion of anticolimits, which provide a…

Category Theory · Mathematics 2024-01-31 Calin Tataru , Jamie Vicary

Centers of categories capture the natural operations on their objects. Homotopy coherent centers are introduced here as an extension of this notion to categories with an associated homotopy theory. These centers can also be interpreted as…

Algebraic Topology · Mathematics 2019-04-12 Markus Szymik

We prove an ambidexterity result for $\infty$-categories of $\infty$-categories admitting a collection of colimits. This unifies and extends two known phenomena: the identification of limits and colimits of presentable $\infty$-categories…

Category Theory · Mathematics 2026-03-12 Shay Ben-Moshe

We introduce the quantum isomeric supercategory and the quantum affine isomeric supercategory. These diagrammatically defined supercategories, which can be viewed as isomeric analogues of the HOMFLYPT skein category and its affinization,…

Quantum Algebra · Mathematics 2024-05-15 Alistair Savage

To any affine scheme with a $\mathbb{G}_m$-action, we provide a Bousfield colocalization on the equivariant derived category of modules by constructing, via homotopical methods, an idempotent integral kernel. This endows the equivariant…

Algebraic Geometry · Mathematics 2017-10-05 Matthew R. Ballard , Colin Diemer , David Favero

In a previous article, we introduced notions of finiteness obstruction, Euler characteristic, and L^2-Euler characteristic for wide classes of categories. In this sequel, we prove the compatibility of those notions with homotopy colimits of…

Algebraic Topology · Mathematics 2011-03-28 Thomas M. Fiore , Wolfgang Lück , Roman Sauer

Let $\mathcal A$ be a Hom-finite abelian category with enough projectives. In this note, we show that any covariantly finite $\tau$-rigid subcategory is contained in a support $\tau$-tilting subcategory. We also show that support…

Representation Theory · Mathematics 2023-02-07 Yu Liu , Panyue Zhou

We develop cohomological and homological theories for a profinite group $G$ with coefficients in the Pontryagin dual categories of pro-discrete and ind-profinite $G$-modules, respectively. The standard results of group (co)homology hold for…

Group Theory · Mathematics 2016-09-30 Marco Boggi , Ged Corob Cook

The set of all closed subgroups of a profinite carries a natural profinite topology. This space of subgroups can be classified up to homeomorphism in many cases, and tight bounds placed on its complexity as expressed by its scattered…

Group Theory · Mathematics 2008-09-30 Paul Gartside , Michael Smith

We propose a definition of higher inductive types in $(\infty,1)$-categories with finite limits. We show that the $(\infty,1)$-category of $(\infty,1)$-categories with higher inductive types is finitarily presentable. In particular, the…

Category Theory · Mathematics 2024-10-24 Taichi Uemura

We study extensively the homotopy theory of coalgebras. By coalgebras, we mean the full theory of coalgebras: with counits and not necessarily locally conilpotent. For example $\mathcal E_\infty$-coalgebras, $\mathcal A_\infty$-coalgebras,…

Algebraic Topology · Mathematics 2022-03-11 Brice Le Grignou , Damien Lejay

Let $G$ be a semisimple simply-connected algebraic group over an algebraically closed field of characteristic zero. We prove that the affine Hecke category associated to the loop group of $G$ is equivalent to the colimit, evaluated in the…

Representation Theory · Mathematics 2021-03-31 James Tao , Roman Travkin

In this paper, we justify and make precise an elementary approach that establishes the existence of (co)limits in $\mathbf{Cat}$. This approach, while conceptually evident, has not been made fully explicit or systematically described in the…

Category Theory · Mathematics 2026-04-16 Varinderjit Mann

We provide, among other things: (i) a Bousfield--Kan formula for colimits in $\infty$-categories (generalizing the 1-categorical formula for a colimit as a coequalizer of maps between coproducts); (ii) $\infty$-categorical generalizations…

Algebraic Topology · Mathematics 2015-10-15 Aaron Mazel-Gee