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In this paper, we define the notion of closed models defined by counting, and we compute their homotopy categories. We apply this construction to various categories of graphs. We show that there does not exist a closed model in the category…

Category Theory · Mathematics 2017-04-04 Tsemo Aristide

We construct a Quillen model structure on the category of spectral categories, where the weak equivalences are the symmetric spectra analogue of the notion of equivalence of categories.

K-Theory and Homology · Mathematics 2009-02-23 Goncalo Tabuada

An n-category is some sort of algebraic structure consisting of objects, morphisms between objects, 2-morphisms between morphisms, and so on up to n-morphisms, together with various ways of composing them. We survey various concepts of…

q-alg · Mathematics 2008-02-03 John C. Baez

We demonstrate that the proper homotopy equivalence relation for locally finite graphs is Borel complete. Furthermore, among the infinite graphs, there is a comeager equivalence class. As corollaries, we obtain the analogous results for the…

Logic · Mathematics 2025-11-13 Hannah Hoganson , Jenna Zomback

To characterize categorical constraints - associativity, commutativity and monoidality - in the context of quasimonoidal categories, from a cohomological point of view, we define the notion of a parity (quasi)complex. Applied to groups…

Category Theory · Mathematics 2007-05-23 Lucian M. Ionescu

Recently there has been growing interest in discrete homotopies and homotopies of graphs beyond treating graphs as 1-dimensional simplicial spaces. One such type of homotopy is $\times$-homotopy. Recent work by Chih-Scull has developed a…

Combinatorics · Mathematics 2025-04-22 Keira Behal , Tien Chih

We show that the category of simplicial sets is a co-reflective subcategory of the category of cubical sets with connections, with the inclusion given by a version of the straightening functor. We show that using the co-reflector, one can…

Category Theory · Mathematics 2019-06-24 Chris Kapulkin , Zachery Lindsey , Liang Ze Wong

Topologists are sometimes interested in space-valued diagrams over a given index category, but it is tricky to say what such a diagram even is if we look for a notion that is stable under equivalence. The same happens in (homotopy) type…

Logic · Mathematics 2017-04-18 Nicolai Kraus , Christian Sattler

In this paper we construct a cofibrantly generated model category structure on the category of all small symmetric multicategories enriched in simplicial sets.

Algebraic Topology · Mathematics 2011-11-18 Marcy Robertson

We prove that the $\infty$-category of orthogonal factorization systems embeds fully faithfully into the $\infty$-category of double $\infty$-categories. Moreover, we prove an (un)straightening equivalence for double $\infty$-categories,…

Category Theory · Mathematics 2025-01-03 Branko Juran

Let $\mathcal{E}$ be a weakly idempotent complete exact category with enough injective and projective objects. Assume that $\mathcal{M} \subseteq \mathcal{E}$ is a rigid, contravariantly finite subcategory of $\mathcal{E}$ containing all…

Representation Theory · Mathematics 2019-05-07 Lucie Jacquet-Malo

In this paper we analyze some relationships between the topological complexity of a space $X$ and the category of $C_{\Delta_X},$ the homotopy cofibre of the diagonal map $\Delta_X:X\rightarrow X\times X.$ We establish the equality of the…

Algebraic Topology · Mathematics 2012-02-23 J. Calcines , L. Vandembroucq

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

We consider categories of relational structures that fully embed every category of universal algebras, and prove a partial characterisation of these in terms of an infinitary variant of the notion of nowhere density of Ne\v{s}et\v{r}il and…

Logic · Mathematics 2023-03-24 Ioannis Eleftheriadis

We introduce affine structures on groups and show they form a category equivalent to that of semi-braces. In particular, such a new description of semi-braces includes that presented by Rump for braces. By specific affine structures, we…

Group Theory · Mathematics 2025-05-02 Paola Stefanelli

In categories of linear relations between finite dimensional vector spaces, composition is well-behaved only at pairs of relations satisfying transversality and monicity conditions. A construction of Wehrheim and Woodward makes it possible…

Symplectic Geometry · Mathematics 2015-03-24 Alan Weinstein

Let $\mathbb{k}$ be a commutative ring with global dimension zero. We show that we can rigidify homotopy coherent comodules in connective modules over the Eilenberg-Mac Lane spectrum of $\mathbb{k}$. That is, the $\infty$-category of…

Algebraic Topology · Mathematics 2024-04-09 Maximilien Péroux

Badzioch showed that in the category of simplicial sets each homotopy algebra of a Lawvere theory is weakly equivalent to a strict algebra. In seeking to extend this result to other contexts Rosicky observed a key point to be that each…

Category Theory · Mathematics 2022-01-31 John Bourke

We present different ways of endowing a particular category of graphs with Quillen model structures. We show, among other things, that the core of a graph can be seen as its homotopy type in an appropriate Quillen model structure, and that…

Combinatorics · Mathematics 2012-09-13 Jean-Marie Droz

In this paper, we characterize the second bounded characteristic classes of foliated bundles in terms of the non-descendible quasi-morphisms on the universal covering of the structure group. As its application, we study the boundedness of…

Symplectic Geometry · Mathematics 2022-03-16 Morimichi Kawasaki , Shuhei Maruyama