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We introduce the notion of `bar category' by which we mean a monoidal category equipped with additional structure formalising the notion of complex conjugation. Examples of our theory include bimodules over a $*$-algebra, modules over a…

Quantum Algebra · Mathematics 2007-12-23 E. J. Beggs , S. Majid

In this paper, we introduce the category of brace triples in a braided monoidal setting and prove that it is isomorphic to the category of s-Hopf braces, which are a generalization of cocommutative Hopf braces. After that, we obtain a…

Rings and Algebras · Mathematics 2025-04-15 José Manuel Fernández Vilaboa , Ramón González Rodríguez , Brais Ramos Pérez

The problem of determining gauge and monoidal equivalence classes of fusion categories is considered from the perspective of geometric invariant theory. It is shown that the gauge (or monoidal) class of a fusion category is determined by…

Quantum Algebra · Mathematics 2015-09-11 Tobias Hagge , Matthew Titsworth

Braid groups are an important and flexible tool used in several areas of science, such as Knot Theory (Alexander's theorem), Mathematical Physics (Yang-Baxter's equation) and Algebraic Geometry (monodromy invariants). In this note we will…

Algebraic Geometry · Mathematics 2019-05-10 Francesco Polizzi

In this paper, we state the notion of morphisms in the category of abelian crossed modules and prove that this category is equivalent to the category of strict Picard categories and regular symmetric monoidal functors. The theory of…

Group Theory · Mathematics 2013-09-13 Nguyen Tien Quang , Che Thi Kim Phung , Ngo Sy Tung

We begin with a brief sketch of what is known and conjectured concerning braided monoidal 2-categories and their applications to 4d topological quantum field theories and 2-tangles (surfaces embedded in 4-dimensional space). Then we give…

q-alg · Mathematics 2020-11-23 John C. Baez , Martin Neuchl

In this article, we give a numerical algorithm to compute braid groups of curves, hyperplane arrangements, and parameterized system of polynomial equations. Our main result is an algorithm that determines the cross-locus and the generators…

Geometric Topology · Mathematics 2017-11-22 Jose Israel Rodriguez , Botong Wang

We give a monoidal presentation of Coxeter and braid 2-groups, in terms of decorated planar graphs. This presentation extends the Coxeter presentation. We deduce a simple criterion for a Coxeter group or braid group to act on a category.

Representation Theory · Mathematics 2017-01-11 Ben Elias , Geordie Williamson

Butz and Moerdijk famously showed that every (Grothendieck) topos with enough points is equivalent to the category of sheaves on some topological groupoid. We give an alternative, more algebraic construction in the special case of a topos…

Category Theory · Mathematics 2019-06-07 Jens Hemelaer

We compare three different ways of defining group cohomology with coefficients in a crossed-module: 1) explicit approach via cocycles; 2) geometric approach via gerbes; 3) group theoretic approach via butterflies. We discuss the case where…

K-Theory and Homology · Mathematics 2010-01-26 Behrang Noohi

In this paper we study grouplike monoids, these are monoids that contain a group to which we add an ordered set of idempotents. We classify finite categories with two objects having grouplike endomorphism monoids, and we give a count of…

Category Theory · Mathematics 2022-10-10 Najwa Ghannoum

Using a homological invariant together with an obstruction class in a certain Ext^2-group, we may classify objects in triangulated categories that have projective resolutions of length two. This invariant gives strong classification results…

Operator Algebras · Mathematics 2017-04-20 Rasmus Bentmann , Ralf Meyer

In this article we investigate which categorical structures of a category C are inherited by its arrow category. In particular, we show that a monoidal equivalence between two categories gives rise to a monoidal equivalence between their…

Category Theory · Mathematics 2023-09-28 Paulina L. A. Goedicke , Jamie Vicary

Let G be a unipotent algebraic group over an algebraically closed field k of characteristic p > 0 and let l be a prime different from p. Let e be a minimal idempotent in D_G(G), the braided monoidal category of G-equivariant (under…

Representation Theory · Mathematics 2013-12-17 Tanmay Deshpande

In this paper using split extensions of group-groupoids we obtain the notion of crossed modules over group-grouoids which are also called 2-groups and we prove a categorical equivalence of these types of crossed modules and double…

Category Theory · Mathematics 2021-02-16 Sedat Temel , Tunçar Şahan , Osman Mucuk

The structure of a $k$-fold monoidal category as introduced by Balteanu, Fiedorowicz, Schw\"anzl and Vogt can be seen as a weaker structure than a symmetric or even braided monoidal category. In this paper we show that it is still…

Algebraic Topology · Mathematics 2007-05-23 Stefan Forcey , Jacob Siehler , Seth Sowers

We propose a new model for multicategories with symmetries with respect to Zhang's group operads. The fully faithful embedding of the category of group operads into that of crossed interval groups is made use of, and it is shown that every…

Category Theory · Mathematics 2018-07-06 Jun Yoshida

We study braided Hochschild and cyclic homology of ribbon algebras in braided monoidal categories, as introduced by Baez and by Akrami and Majid. We compute this invariant for several examples coming from quantum groups and braided groups.

Quantum Algebra · Mathematics 2010-08-13 Tom Hadfield , Ulrich Kraehmer

We describe the multiplicative structures that arise on categories of equivariant modules over certain equivariant commutative ring spectra. Building on our previous work on N-infinity ring spectra, we construct categories of equivariant…

Algebraic Topology · Mathematics 2019-08-07 Andrew J. Blumberg , Michael A. Hill

We introduce simple models for associative algebras and bimodules in the context of non-symmetric $\infty$-operads, and use these to construct an $(\infty,2)$-category of associative algebras, bimodules, and bimodule homomorphisms in a…

Algebraic Topology · Mathematics 2020-11-03 Rune Haugseng