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We study the accessibility properties of trivial cofibrations and weak equivalences in a combinatorial model category and prove an estimate for the accessibility rank of weak equivalences. In particular, we show that the class of weak…

Algebraic Topology · Mathematics 2015-05-13 G. Raptis , J. Rosický

We show that basic homotopical notions such as homotopy sets and groups, connected and truncated maps, cellular constructions and skeleta, etc., extend to the setting of $(\infty,\infty)$-categories, as well as to presentable categories…

Algebraic Topology · Mathematics 2026-04-16 David Gepner , Hadrian Heine

The Schur orthogonality relations are a cornerstone in the representation theory of groups. We utilize a generalization to weak Hopf algebras to provide a new, readily verifiable condition on the skeletal data for deciding whether a given…

Quantum Algebra · Mathematics 2024-02-06 Jacob C. Bridgeman , Laurens Lootens , Frank Verstraete

The homotopy category of a model structure on a weakly idempotent complete additive category is proved to be equivalent to the additive quotient of the category of cofibrant-fibrant objects with respect to the subcategory of…

Representation Theory · Mathematics 2025-01-28 Xue-Song Lu , Pu Zhang

We consider categories of posets with $\mathfrak{C}$-valued structure sheaves for any category $\mathfrak{C}$ and see how they possess poset-indexed lax colimits that are both easy to describe and "weakly equivalent" to their ordinary…

Algebraic Geometry · Mathematics 2023-01-10 J. Sánchez González

Given a family $\F$ of posets closed under disjoint unions and the operation of taking convex subposets, we construct a category $\C_{\F}$ called the \emph{incidence category of $\F$}. This category is "nearly abelian" in the sense that all…

Quantum Algebra · Mathematics 2009-10-29 Matt Szczesny

We introduce two new partial orders on the standard Young tableaux of a given partition shape, in analogy with the strong and weak Bruhat orders on permutations. Both posets are ranked by the major index statistic offset by a fixed shift.…

Combinatorics · Mathematics 2020-05-19 Sara C. Billey , Matjaž Konvalinka , Joshua P. Swanson

In this mostly expository paper, we present recent progress on infinite (weak) cluster categories that are related to triangulations of the disk, with and without a puncture. First we recall the notion of a cluster category. Then we move to…

Representation Theory · Mathematics 2025-06-19 Fatemeh Mohammadi , Job Daisie Rock , Francesca Zaffalon

We affirm and generalize a conjecture of Blumberg and Hill: unital weak $\mathcal{N}_\infty$-operads are closed under $\infty$-categorical Boardman-Vogt tensor products and the resulting tensor products correspond with joins of weak…

Algebraic Topology · Mathematics 2025-08-07 Natalie Stewart

Palu defined the index with respect to a cluster tilting object in a suitable triangulated category, in order to better understand the Caldero-Chapoton map that exhibits the connection between cluster algebras and representation theory. We…

Representation Theory · Mathematics 2024-08-23 Peter Jørgensen , Amit Shah

In this paper we address the problem of classification of simple weight modules over weak generalized Weyl algebras of rank one. The principal difference between weak generalized Weyl algebras and generalized weight algebras is that weak…

Representation Theory · Mathematics 2017-05-10 Rencai Lu , Volodymyr Mazorchuk , Kaiming Zhao

A finite tensor category is called pointed if all its simple objects are invertible. We find necessary and sufficient conditions for two pointed semisimple categories to be dual to each other with respect to a module category. Whenever the…

Quantum Algebra · Mathematics 2009-12-19 Deepak Naidu

Many definitions of weak and strict $\infty$-categories have been proposed. In this paper we present a definition for $\infty$-categories with strict associators, but which is otherwise fully weak. Our approach is based on the existing type…

Category Theory · Mathematics 2021-09-06 Eric Finster , Alex Rice , Jamie Vicary

Cluster algebras are categorified by cluster categories, and $g$-vectors are categorified by the classic index with respect to cluster tilting subcategories. However, the recently introduced completed discrete cluster categories of Dynkin…

Representation Theory · Mathematics 2024-12-17 Francesca Fedele , Peter Jorgensen , Amit Shah

In this paper we introduce the notion of weak operator and the theory of Yetter-Drinfeld modules over a weak braided Hopf algebra with invertible antipode in a strict monoidal category. We prove that the class of such objects constitutes a…

We introduce hom-associative Ore extensions as non-unital, non-associative Ore extensions with a hom-associative multiplication, and give some necessary and sufficient conditions when such exist. Within this framework, we construct families…

Rings and Algebras · Mathematics 2020-04-16 Per Bäck , Johan Richter , Sergei Silvestrov

We extend the weak Bruhat order of a finite Coxeter group to the set of its coclasses, modulo parabolic standard subgroups. We use this order to describe associative algebra structures on the vector spaces spanned by the faces of…

Combinatorics · Mathematics 2007-05-23 Patricia Palacios , Maria Ronco

Let $S$ be a pomonoid. In this paper, {\bf Pos}-$S$, the category of $S$-posets and $S$-poset maps, is considered. One of the main aims of this paper is to draw attention to the notion of weak factorization systems in {\bf Pos}-$S.$ We show…

Category Theory · Mathematics 2015-04-08 Farideh Farsad , Ali Madanshekaf

A weak entwining structure in a 2-category K consists of a monad t and a comonad c, together with a 2-cell relating both structures in a way that generalizes a mixed distributive law.A weak entwining structure can be characterized as a…

Category Theory · Mathematics 2010-09-21 Gabriella Böhm

We introduce partially ordered sets (posets) with an additional structure given by a collection of vector subspaces of an algebra $A$. We call them algebraically equipped posets. Some particular cases of these, are generalized equipped…

Representation Theory · Mathematics 2015-01-14 Raymundo Bautista , Ivon Dorado