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We provide a new characterization of enriched accessible categories by introducing the two new notions of virtual reflectivity and virtual orthogonality as a generalization of the usual reflectivity and orthogonality conditions for locally…

Category Theory · Mathematics 2022-07-29 Stephen Lack , Giacomo Tendas

We define two different versions of the relative De Rham cohomology groups of a diffeological space. Additionally, we study a variant of the Mayer-Vietoris sequence and discuss the existence of a relative cup product. Our approach is…

Algebraic Topology · Mathematics 2024-12-19 Enrique Macías-Virgós , Reihaneh Mehrabi

Let $V$ be a finite dimensional $k$-vector space, where $k$ is an algebraic closed field of characteristic zero. Let $G \subseteq \mathrm{SL}(V)$ be a finite abelian group, and denote by $S$ the $G$-invariant subring of the polynomial ring…

Algebraic Geometry · Mathematics 2025-10-20 Xiaojun Chen , Jieheng Zeng

We establish a unified group-theoretic framework bridging the arithmetic homotopy exact sequence of a variety and the Birman exact sequence of a surface. Within this framework, we reinterpret classical arithmetic notions - such as the…

Algebraic Geometry · Mathematics 2025-12-24 Miltiadis Karakikes , Sotiris Karanikolopoulos , Aristides Kontogeorgis , Dimitrios Noulas

We introduce the notion of a relative pseudomonad, which generalises the notion of a pseudomonad, and define the Kleisli bicategory associated to a relative pseudomonad. We then present an efficient method to define pseudomonas on the…

Category Theory · Mathematics 2019-05-16 Marcelo Fiore , Nicola Gambino , Martin Hyland , Glynn Winskel

We develop the notion of deformation of a morphism in a left-proper model category. As an application we provide a geometric/homotopic description of deformations of commutative (non-positively) graded differential algebras over a local…

Category Theory · Mathematics 2020-01-27 Marco Manetti , Francesco Meazzini

We give an explicit combinatorial description of the deformation theory of the Abelian category of (quasi)coherent sheaves on any separated Noetherian scheme $X$ via the deformation theory of path algebras of quivers with relations, by…

Algebraic Geometry · Mathematics 2023-12-08 Severin Barmeier , Zhengfang Wang

Let $A \leq G$ be a subgroup of a group $G$. An $A$-complement of $G$ is a subgroup $H$ of $G$ such that $G = A H$ and $A \cap H = \{1\}$. The \emph{classifying complements problem} asks for the description and classification of all…

Group Theory · Mathematics 2015-12-01 A. L. Agore , G. Militaru

In the present article, we investigate a possibility of a real-valued map on the space of tuples of commuting trace-class self-adjoint operators, which behaves like the usual trace map on the space of trace-class linear operators. It turns…

Operator Algebras · Mathematics 2008-03-26 Sung Myung

The 2-category V-Cat of categories enriched over a braided monoidal category V is not itself braided in any way that is based upon the braiding of V. The exception is the case in which V is symmetric, which leads to V-Cat being symmetric as…

Category Theory · Mathematics 2007-05-23 Stefan Forcey

We consider notions of metrized categories, and then approximate categorical structures defined by a function of three variables generalizing the notion of $2$-metric space. We prove an embedding theorem giving sufficient conditions for an…

Category Theory · Mathematics 2015-11-06 Abdelkrim Aliouche , Carlos Simpson

Let K >= 1 be a parameter. A K-approximate group is a finite set A in a (local) group which contains the identity, is symmetric, and such that A^2 is covered by K left translates of A. The main result of this paper is a qualitative…

Group Theory · Mathematics 2011-10-26 Emmanuel Breuillard , Ben Green , Terence Tao

We investigate equivalences between the categories of perfects complexes of the quotients of two smooth projective schemes by the action of a finite group. As a result we give a necessary and sufficient condition for an equivalence between…

Algebraic Geometry · Mathematics 2019-02-14 Francesco Amodeo , Riccardo Moschetti , Mattia Ornaghi

The 2-categories of strict 2-groups and crossed modules are introduced and their 2-equivalence is made explicit.

Category Theory · Mathematics 2008-12-09 Sven-S. Porst

We propose a geometric and categorical approach to the Hodge Conjecture for all smooth projective complex varieties. By embedding any such variety into a flat family with general fibers smooth complete intersections, we prove the conjecture…

Algebraic Geometry · Mathematics 2025-08-15 Karim Mansour

Inverse categories are categories in which every morphism x has a unique pseudo-inverse y in the sense that xyx=x and yxy=y. Persistence modules from topological data analysis and similarly decomposable category representations factor…

Category Theory · Mathematics 2021-01-15 Sanjeevi Krishnan , Crichton Ogle

We introduce a notion of a filtered model structure and use this notion to produce various model structures on pro-categories. This framework generalizes several known examples. We give several examples, including a homotopy theory for…

Algebraic Topology · Mathematics 2007-05-23 Halvard Fausk , Daniel C. Isaksen

We introduce the notions of proto-complete, complete, complete* and strong-complete objects in pointed categories. We show under mild conditions on a pointed exact protomodular category that every proto-complete (respectively complete)…

Category Theory · Mathematics 2021-02-22 James Richard Andrew Gray

It is well-known that reduced smooth orbifolds and proper effective foliation Lie groupoids form equivalent categories. However, for certain recent lines of research, equivalence of categories is not sufficient. We propose a notion of maps…

Geometric Topology · Mathematics 2015-09-10 Anke D. Pohl

We relativize the notion of a compact object in an abelian category with respect to a fixed subclass of objects. We show that the standard closure properties persist to hold in this case. Furthermore, we describe categorical and…

Category Theory · Mathematics 2017-06-27 Peter Kálnai , Jan Žemlička