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Using full images of accessible functors, we prove some results about combinatorial and accessible model categories. In particular, we give an example of a weak factorization system on a locally presentable category which is not accessible.

Category Theory · Mathematics 2022-02-08 Jiří Rosický

We survey the extensions of a group by a group using crossed products instead of exact sequences of groups. The approach has various advantages, one of them being that the crossed product is an universal object. Several new applications are…

Group Theory · Mathematics 2014-03-18 A. L. Agore , G. Militaru

We investigate the categories of weak maps associated to an algebraic weak factorisation system (AWFS) in the sense of Grandis-Tholen. For any AWFS on a category with an initial object, cofibrant replacement forms a comonad, and the…

Category Theory · Mathematics 2015-09-15 John Bourke , Richard Garner

Weak bisimilarity is a distribution-based equivalence notion for Markov automata. It has gained some popularity as the coarsest reasonable behavioural equivalence on Markov automata. This paper studies a strictly coarser notion: Late weak…

Formal Languages and Automata Theory · Computer Science 2014-01-15 Christian Eisentraut , Jens Chr. Godskesen , Holger Hermanns , Lei Song , Lijun Zhang

The small object argument is a transfinite construction which, starting from a set of maps in a category, generates a weak factorisation system on that category. As useful as it is, the small object argument has some problematic aspects: it…

Category Theory · Mathematics 2011-10-17 Richard Garner

In braided tensor categories we show the Maschke's theorem and give the necessary and sufficient conditions for double cross biproducts and crossbiproducts and biproducts to be bialgebras. We obtain the factorization theorem for braided…

Rings and Algebras · Mathematics 2007-11-06 Shouchuan Zhang

Motivated by the universal obstruction to the deformation quantization of Poisson structures in infinite dimensions we introduce the notion of quantizable odd Lie bialgebra. The main result of the paper is a construction of a highly…

Quantum Algebra · Mathematics 2016-08-24 Anton Khoroshkin , Sergei Merkulov , Thomas Willwacher

We introduce the notion of a crossed product of an algebra by a coalgebra $C$, which generalises the notion of a crossed product by a bialgebra well-studied in the theory of Hopf algebras. The result of such a crossed product is an algebra…

q-alg · Mathematics 2008-02-03 Tomasz Brzezinski

A braided category of C*-algebras is constructed. Its objects are C*-algebras endowed with an action of the group R, its morphisms are C*-algebras morphisms intertwining the action of R, the crossed product of its two objects essentially…

q-alg · Mathematics 2009-10-30 Malgorzata Rowicka-Kudlicka

In this paper, I introduce weak representations of a Lie groupoid $G$. I also show that there is an equivalence of categories between the categories of 2-term representations up to homotopy and weak representations of $G$. Furthermore, I…

Differential Geometry · Mathematics 2017-04-18 Seth Wolbert

Two cochain complexes are constructed for an algebra A and a coalgebra C entwined with each other via the map $\psi:C\otimes A\to A\otimes C$. One complex is associated to an A-bimodule, the other to a C-bicomodule. In the former case the…

Rings and Algebras · Mathematics 2007-05-23 Tomasz Brzezinski

Using a coupling argument, we establish a general weak law of large numbers for functionals of binomial point processes in d-dimensional space, with a limit that depends explicitly on the (possibly non-uniform) density of the point process.…

Probability · Mathematics 2007-05-23 Mathew D. Penrose , J. E. Yukich

We define fake weighted projective spaces as a generalisation of weighted projective spaces. We introduce the notions of fundamental group in codimension 1 and of universal covering in codimension 1. We prove that for every fake weighted…

Algebraic Geometry · Mathematics 2008-05-09 Weronika Buczynska

In the note some construction of Lie algebras is introduced. It is proved that the construction has the same property as a well known wreath product of groups [1]: Any extension of groups can be embedded into their wreath product [2].

Rings and Algebras · Mathematics 2011-07-08 Lev Simonian

We introduce a general theory of twisting algebraic structures based on actions of a bialgebra. These twists are closely related to algebraic deformations and also to the theory of quasi-triangular bialgebras. In particular, a deformation…

High Energy Physics - Theory · Physics 2008-02-03 Anthony Giaquinto , J. J. Zhang

A weak mixed distributive law (also called weak entwining structure) in a 2-category consists of a monad and a comonad, together with a 2-cell relating them in a way which generalizes a mixed distributive law due to Beck. We show that a…

Category Theory · Mathematics 2012-01-27 Gabriella Böhm , Stephen Lack , Ross Street

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

We characterize those varieties of universal algebras where every split epimorphism considered as a map of sets is a product projection. In addition we obtain new characterizations of protomodular, unital and subtractive varieties as well…

Category Theory · Mathematics 2012-08-13 James R. A. Gray , Nelson Martins-Ferreira

A set of valuable universal similarity factorization equalities are established over complex Clifford algebras $\Cn.$ Through them matrix representations of complex Clifford algebras $\Cn$ can directly be derived, and their properties can…

Rings and Algebras · Mathematics 2007-05-23 Yongge Tian

Looking at bivariate copulas from the perspective of conditional distributions and considering weak convergence of almost all conditional distributions yields the notion of weak conditional convergence. At first glance, this notion of…

Statistics Theory · Mathematics 2020-10-12 Thimo M. Kasper , Sebastian Fuchs , Wolfgang Trutschnig