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We present an intrinsic and concrete development of the subdivision of small categories, give some simple examples and derive its fundamental properties. As an application, we deduce an alternative way to compare the homotopy categories of…

Algebraic Topology · Mathematics 2018-07-10 Matias Luis del Hoyo

We investigate the extent to which the weak equivalences in a model category can be equipped with algebraic structure. We prove, for instance, that there exists a monad T such that a morphism of topological spaces admits T-algebra structure…

Category Theory · Mathematics 2022-01-31 John Bourke

Staton has shown that there is an equivalence between the category of presheaves on (the opposite of) finite sets and partial bijections and the category of nominal restriction sets: see [2, Exercise 9.7]. The aim here is to see that this…

Logic in Computer Science · Computer Science 2014-01-31 Andrew M. Pitts

We develop the homotopy theory of semisimplicial sets constructively and without reference to point-set topology to obtain a constructive model for $\omega$-groupoids. Most of the development is folklore, but for a few results the author is…

Category Theory · Mathematics 2018-10-01 Christian Sattler

Presentations of categories are a well-known algebraic tool to provide descriptions of categories by means of generators, for objects and morphisms, and relations on morphisms. We generalize here this notion, in order to consider situations…

Logic in Computer Science · Computer Science 2019-03-14 Pierre-Louis Curien , Samuel Mimram

Louveau and Rosendal [5] have shown that the relation of bi-embeddability for countable graphs as well as for many other natural classes of countable structures is complete under Borel reducibility for analytic equivalence relations. This…

Logic · Mathematics 2011-12-05 Sy-David Friedman , Luca Motto Ros

This paper gives a uniform-theoretic refinement of classical homotopy theory. Both cubical sets (with connections) and uniform spaces admit classes of weak equivalences, special cases of classical weak equivalences, appropriate for the…

Algebraic Topology · Mathematics 2021-09-20 Sanjeevi Krishnan , Crichton Ogle

We consider reducibility of equivalence relations (ERs, for brevity), in a nonstandard domain, in terms of the Borel reducibility and the countably determined (CD, for brevity) reducibility. This reveals phenomena partially analogous to…

Logic · Mathematics 2018-08-16 Vladimir Kanovei , Michael Reeken

We show that pointlike sets are decidable for the pseudovariety of finite semigroups whose idempotent-generated subsemigroup is R-trivial. Notably, our proof is constructive: we provide an explicit relational morphism which computes the…

Group Theory · Mathematics 2022-04-21 Karsten Henckell , Samuel Herman

We look at equivalence relations on the set of models of a theory -- MERs, for short -- such that the class of equivalent pairs is itself an elementary class, in a language appropriate for pairs of models. We provide many examples of…

Logic · Mathematics 2025-07-24 Michael Benedikt , Ehud Hrushovski

It is well-known that small categories have equivalent descriptions as partial monoids. We provide a formulation of partial monoid and partial monoid homomorphism involving $s$ and $t$ instead of identities and then following a recent…

Category Theory · Mathematics 2015-03-02 Rachel A. D. Martins

In this paper we put a cofibrantly generated model category structure on the category of small simplicial categories. The weak equivalences are a simplicial analogue of the notion of equivalence of categories.

Algebraic Topology · Mathematics 2007-05-23 Julia E. Bergner

While most network embedding techniques model the proximity between nodes in a network, recently there has been significant interest in structural embeddings that are based on node equivalences, a notion rooted in sociology: equivalences or…

Social and Information Networks · Computer Science 2021-01-15 Junchen Jin , Mark Heimann , Di Jin , Danai Koutra

We construct a category equivalent to the category $\mathbf{Mon}$ of monoids and monoid homomorphisms, based on categories with strict factorization systems. This equivalence is then extended to the category $\mathbf{Mon_s}$ of unital…

Category Theory · Mathematics 2025-10-31 Xavier Mary

The paper establishes an equivalence between directed homotopy categories of (diagrams of) cubical sets and (diagrams of) directed topological spaces. This equivalence both lifts and extends an equivalence between classical homotopy…

Algebraic Topology · Mathematics 2026-02-02 Sanjeevi Krishnan

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 construct ergodic discrete probability measure preserving equivalence relations $\cR$ that has no proper ergodic normal subequivalence relations and no proper ergodic finite-index subequivalence relations. We show that every treeable…

Dynamical Systems · Mathematics 2015-08-11 Lewis Bowen

We proved in a previous work that Cattani-Sassone's higher dimensional transition systems can be interpreted as a small-orthogonality class of a topological locally finitely presentable category of weak higher dimensional transition…

Category Theory · Mathematics 2014-01-31 Philippe Gaucher

Invertibility is an important concept in category theory. In higher category theory, it becomes less obvious what the correct notion of invertibility is, as extra coherence conditions can become necessary for invertible structures to have…

Category Theory · Mathematics 2020-10-20 Alex Rice

We study the structure of the category of representations of $\mathbf{FA}$, the category of finite sets and all maps, mostly working over a field of characteristic zero. This category is not semi-simple and exhibits interesting features. We…

Representation Theory · Mathematics 2025-09-16 Geoffrey Powell
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