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The present paper links the representation theory of Lie groupoids and infinite-dimensional Lie groups. We show that smooth representations of Lie groupoids give rise to smooth representations of associated Lie groups. The groups envisaged…

Group Theory · Mathematics 2019-05-21 Habib Amiri , Alexander Schmeding

We introduce a linearly ordered lattice $\mu(Grp)$ of torsion theories in simplicial groups. The torsion theories are defined where the torsion/torsion-free subcategories are given by the simplicial groups with bounded above/below Moore…

Category Theory · Mathematics 2022-02-16 Guillermo López Cafaggi

We prove a conjecture of Bahri, Bendersky, Cohen and Gitler: if K is a shifted simplicial complex on n vertices, X_1,..., X_n are spaces and CX_i is the cone on X_i, then the polyhedral product determined by K and the pairs (CX_i,X_i) is…

Algebraic Topology · Mathematics 2011-10-21 Jelena Grbic , Stephen Theriault

We consider the path space of a curved manifold on which a point particle is introduced in a conservative physical system with constant total energy to formulate its action functional and geodesic equation together with breaks on the path.…

Mathematical Physics · Physics 2007-06-04 Yong Seung Cho , Soon-Tae Hong

Let $f:G\rightarrow H$ be a homomorphism of groups, we construct a topological space $X_f$ such that its group of homeomorphisms is isomorphic to $G$, its group of homotopy classes of self-homotopy equivalences is isomorphic to $H$ and the…

Algebraic Topology · Mathematics 2021-04-16 Pedro J. Chocano , Manuel A. Morón , Francisco R. Ruiz del Portal

We build a concrete and natural model for the strict 2-category of orbifolds. In particular we prove that if one localizes the 2-category of proper etale Lie groupoids at a class of 1-arrows that we call "covers", then the strict 2-category…

Differential Geometry · Mathematics 2010-09-02 Eugene Lerman

We construct an equivariant version of discrete Morse theory for simplicial complexes endowed with group actions. The key ingredient is a 2-categorical criterion for making acyclic partial matchings on the quotient space compatible with an…

Group Theory · Mathematics 2022-03-02 Naya Yerolemou , Vidit Nanda

Path and boundary-path groupoids of finitely aligned higher-rank graphs are often constructed using either filters or graph morphisms. We generalise the graph morphism approach to finitely aligned P-graphs where (Q, P) is a weakly…

Rings and Algebras · Mathematics 2025-09-18 Lisa Orloff Clark , Malcolm Jones

We give a detailed description of the structure of the actor 2-crossed module related to the automorphisms of a crossed module of groupoids. This generalises work of Brown and Gilbert for the case of crossed modules of groups, and part of…

Category Theory · Mathematics 2007-05-23 R. Brown , I. Icen

This work is a spin-off of an on-going programme which aims at revisiting the original studies of Lie and Cartan on pseudogroups and geometric structures from a modern perspective. Within the framework of Lie groupoids equipped with a…

Differential Geometry · Mathematics 2022-12-02 Luca Accornero , Francesco Cattafi

The purpose of this article is to give an exposition of topological properties of spaces of homomorphisms from certain finitely generated discrete groups to Lie groups $G$, and to describe their connections to classical representation…

Algebraic Topology · Mathematics 2016-09-28 Frederick R. Cohen , Mentor Stafa

We provide a treatment of isomorphism within a set-theoretic formulation of dependent type theory. Type expressions are assigned their natural set-theoretic compositional meaning. Types are divided into small and large types --- sets and…

Logic in Computer Science · Computer Science 2018-01-23 David McAllester

We provide a recursive construction of an acyclic matching (also known as a gradient vector field, an equivalent notion to a discrete Morse function) on the independence complex of a graph with a simplicial vertex using given acyclic…

Combinatorics · Mathematics 2026-04-15 Sucharita Barik , Anupam Mondal , Sajal Mukherjee

We study the homotopy of loops in a fixed path-connected Polish space from a descriptive set-theoretic viewpoint. We show that many analytic equivalence relations arise this way, and many do not. We also study the "free group" over an…

Logic · Mathematics 2025-12-03 Fanxin Wu

In the setting of homotopy type theory, each type can be interpreted as a space. Moreover, given an element of a type, i.e. a point in the corresponding space, one can define another type which encodes the space of loops based at this…

Logic in Computer Science · Computer Science 2024-05-17 Samuel Mimram , Émile Oleon

Morita equivalence classes of Lie groupoids serve as models for differentiable stacks, which are higher spaces in differential geometry, generalizing manifolds and orbifolds. Representations up to homotopy of Lie groupoids provide a higher…

Differential Geometry · Mathematics 2024-10-04 Matias del Hoyo , Cristian Ortiz , Fernando Studzinski

We give a topological interpretation of the core group invariant of a surface embedded in S^4. We show that the group is isomorphic to the free product of the fundamental group of the double branch cover of S^4 with the surface as a…

Geometric Topology · Mathematics 2007-05-23 Jozef H. Przytycki , Witold Rosicki

We explore the connections between automata, groups, limit spaces of self-similar actions, and tilings. In particular, we show how a group acting ``nicely'' on a tree gives rise to a self-covering of a topological groupoid, and how the…

Group Theory · Mathematics 2009-11-27 Laurent Bartholdi , Andre G. Henriques , Volodymyr V. Nekrashevych

Working in the soft-element (classical) viewpoint, we introduce \emph{soft bitopological groups}: soft groups endowed with two soft topologies such that the induced topologies on the set of soft elements make the soft-element group into a…

General Topology · Mathematics 2026-02-16 S. Ray

Given a permutation group acting on coordinates of $\mathbb{R}^n$, we consider lattice-free polytopes that are the convex hull of an orbit of one integral vector. The vertices of such polytopes are called \emph{core points} and they play a…

Metric Geometry · Mathematics 2015-02-24 Katrin Herr , Thomas Rehn , Achill Schürmann