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In this paper, we unify various approaches to generalized covering space theory by introducing a categorical framework in which coverings are defined purely in terms of unique lifting properties. For each category $\mathcal{C}$ of…

Algebraic Topology · Mathematics 2015-09-25 Jeremy Brazas

We provide a general construction of induced $t$-structures, that generalizes standard $t$-structures for $\infty$-categories of sheaves. More precisely, given a presentable $\infty$-category $\mathcal{X}$ and a presentable stable…

Category Theory · Mathematics 2025-04-11 Peter J. Haine , Mauro Porta , Jean-Baptiste Teyssier

The notion of a proper Ellis semigroup compactification is introduced. Ellis's functional approach shows how to obtain them from totally bounded equiuniformities on a phase space $X$ when the acting group $G$ is with the topology of…

General Topology · Mathematics 2025-07-29 K. L. Kozlov , B. V. Sorin

The elementary quotient completion of an elementary doctrine in the sense of Lawvere was introduced in previous work by the first and third authors. It generalises the exact completion of a category with finite products and weak equalisers.…

Logic · Mathematics 2024-10-10 Maria Emilia Maietti , Fabio Pasquali , Giuseppe Rosolini

We use Kan injectivity to axiomatise concepts in the 2-category of topoi. We showcase the expressivity of this language through many examples, and we establish some aspects of the formal theory of Kan extension in this 2-category (pointwise…

Logic · Mathematics 2025-05-22 Ivan Di Liberti , Lingyuan Ye

A general method for lifting weak factorization systems in a category S to model category structures on simplicial objects in S is described, analogously to the lifting of cotorsion pairs in Abelian categories to model category structures…

Algebraic Topology · Mathematics 2021-05-19 Fritz Hörmann

After two papers on weak cubical categories and {\it collarable} cospans, respectively, we put things together and construct a {\it weak} cubical category of cubical {\it collared} cospans of topological spaces. We also build a second…

Algebraic Topology · Mathematics 2008-06-17 Marco Grandis

We study the relationship between presheaf constructions and free cocompletions in the context of formal category theory, elucidating the coincidence between the two concepts in familiar settings. We show that, in a virtual equipment…

Category Theory · Mathematics 2026-04-27 Nathanael Arkor , Dylan McDermott

Quillen defined a {\em model category} to be a category with finite limits and colimits carrying a certain extra structure. In this paper, we show that only finite products and coproducts (in addition to the certain extra structure alluded…

Category Theory · Mathematics 2007-05-23 J. M. Egger

Let G be a discrete group. We give methods to compute for a generalized (co-)homology theory its values on the Borel construction (EG x X)/G of a proper G-CW-complex X satisfying certain finiteness conditions. In particular we give formulas…

K-Theory and Homology · Mathematics 2012-01-24 Michael Joachim , Wolfgang Lueck

We give a general framework of equivariant model category theory. Our groups G, called Hopf groups, are suitably defined group objects in any well-behaved symmetric monoidal category V. For any V, a discrete group G gives a Hopf group,…

Algebraic Topology · Mathematics 2017-09-01 Bertrand Guillou , J. P. May , Jonathan Rubin

We develop a constructive model of homotopy type theory in a Quillen model category that classically presents the usual homotopy theory of spaces. Our model is based on presheaves over the cartesian cube category, a well-behaved…

Algebraic Topology · Mathematics 2026-04-21 Steve Awodey , Evan Cavallo , Thierry Coquand , Emily Riehl , Christian Sattler

Let $X$ be a variety with an action by an algebraic group $G$. In this paper we discuss various properties of $G$-equivariant $D$-modules on $X$, such as the decompositions of their global sections as representations of $G$ (when $G$ is…

Algebraic Geometry · Mathematics 2019-04-11 András C. Lőrincz , Uli Walther

In our previous paper [9], we have introduced topological nearly entropy, Ent_N (f) by restricting X into a class of nearly compact spaces. In the present paper, some additional properties of this notion are studied. Furthermore, we…

Dynamical Systems · Mathematics 2019-08-07 Zabidin Salleh , Syazwani Gulamsarwar

Let $X$ be a $G$-space. In this paper, we introduce the notion of sectional category with respect to $G$. As a result, we obtain $G$-homotopy invariants: the LS category with respect to $G$, the sequential topological complexity with…

Algebraic Topology · Mathematics 2025-05-14 Ramandeep Singh Arora , Navnath Daundkar , Soumen Sarkar

In fairly elementary terms this paper presents, and expands upon, a recent result by Garner by which the notion of topologicity of a concrete functor is subsumed under the concept of total cocompleteness of enriched category theory.…

Category Theory · Mathematics 2016-02-19 Lili Shen , Walter Tholen

We propose the notion of a supercategory as an alternative approach to supermathematics. We show that this setting is rich to carry out many of the basic constructions of supermathematics. We also prove generalizations of a number of…

Quantum Algebra · Mathematics 2008-02-08 Martin Andler , Siddhartha Sahi

For a smooth spacetime $X$, based on the timelike homotopy classes of its timelike paths, we define a topology on $X$ that refines the Alexandrov topology and always coincides with the manifold topology. The space of timelike or causal…

Differential Geometry · Mathematics 2021-08-16 Martin Günther

Given a symmetric monoidal category $C$ with product $\sqcup$, where the neutral element for the product is an initial object, we consider the poset of $\sqcup$-complemented subobjects of a given object $X$. When this poset has finite…

Combinatorics · Mathematics 2025-07-30 Kevin Ivan Piterman , Volkmar Welker

For any length category, we establish a set of rules (necessary and sufficient) that ensure a partial order on the isomorphism classes of simple objects such that the category is equivalent to the category of finite dimensional…

Representation Theory · Mathematics 2026-04-07 Henning Krause