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For all classical groups (and for their analogs in infinite dimension or over general base fields or rings) we construct certain contractions, called "homotopes". The construction is geometric, using as ingredient involutions of associative…

Rings and Algebras · Mathematics 2010-05-31 Wolfgang Bertram , Michael Kinyon

In this work we relate the known results about the homotopy type of classifying spaces for smooth foliations, with the homology and cohomology of the discrete group of diffeomorphisms of a smooth compact connected oriented manifold. The…

Algebraic Topology · Mathematics 2023-11-16 Steven Hurder

In this short note, we provide a calculation of the Euler characteristic of a finite homotopy colimit of finite cell complexes, which depends only on the Euler characteristics of each space and resembles Mobius inversion. Versions of the…

Algebraic Topology · Mathematics 2018-11-07 John D. Berman

Homotopy Type Theory may be seen as an internal language for the $\infty$-category of weak $\infty$-groupoids which in particular models the univalence axiom. Voevodsky proposes this language for weak $\infty$-groupoids as a new foundation…

Category Theory · Mathematics 2019-02-20 Egbert Rijke , Bas Spitters

We study the homotopy theory of locally ordered spaces, that is manifolds with boundary whose charts are partially ordered in a compatible way. Their category is not particularly well-behaved with respect to colimits. However, this category…

Algebraic Topology · Mathematics 2009-12-21 Krzysztof Worytkiewicz

Given a countable group $G$ and two subshifts $X$ and $Y$ over $G$, a continuous, shift-commuting map $\phi : X \to Y$ is called a homomorphism. Our main result states that if every finitely generated subgroup of $G$ has polynomial growth,…

Dynamical Systems · Mathematics 2025-09-10 Robert Bland , Kevin McGoff

Let f: P-->W be an embedding of a compact polyhedron in a closed oriented manifold W, let T be a regular neighborhood of P in W and let C:=closure(W-T) be its complement. Then W is the homotopy push-out of a diagram C<--dT-->P. This…

Algebraic Topology · Mathematics 2014-10-01 Pascal Lambrechts , Don Stanley

We study the homotopy fixed points under the Frobenius endomorphism on the stable $\mathbb A^1$-homotopy category of schemes in characteristic $p>0$ and prove a rigidity result for cellular objects in these categories after inverting $p$.…

Algebraic Geometry · Mathematics 2024-04-08 Timo Richarz , Jakob Scholbach

Nearness theory comes into play in homotopy theory because the notion of closeness between points is essential in determining whether two spaces are homotopy equivalent. While nearness theory and homotopy theory have different focuses and…

Algebraic Topology · Mathematics 2023-06-14 Melih Is , Ismet Karaca

We prove and explain several classical formulae for homotopy (co)limits in general (combinatorial) model categories which are not necessarily simplicially enriched. Importantly, we prove versions of the Bousfield-Kan formula and the fat…

Category Theory · Mathematics 2019-09-04 Sergey Arkhipov , Sebastian Ørsted

Working in the context of symmetric spectra, we describe and study a homotopy completion tower for algebras and left modules over operads in the category of modules over a commutative ring spectrum (e.g., structured ring spectra). We prove…

Algebraic Topology · Mathematics 2014-11-11 John E. Harper , Kathryn Hess

We survey several mathematical developments in the holonomy approach to gauge theory. A cornerstone of this approach is the introduction of group structures on spaces of based loops on a smooth manifold, relying on certain homotopy…

Mathematical Physics · Physics 2022-01-03 Claudio Meneses

We study the homotopy of the connected sum of a manifold with a projective space, viewed as a typical way to stabilize manifolds. In particular, we show a loop homotopy decomposition of a manifold after stabilization by a projective space,…

Algebraic Topology · Mathematics 2023-08-03 Ruizhi Huang , Stephen Theriault

We first show that simply connected co-$H$-spaces and connected $H$-spaces can be uniquely decomposed into prime factors in the homotopy category of pointed $p$-local spaces of finite type, which is used to develop a $p$-local version of…

Algebraic Topology · Mathematics 2019-05-14 Ruizhi Huang , Jie Wu

Any modality in homotopy type theory gives rise to an orthogonal factorization system of which the left class is stable under pullbacks. We show that there is a second orthogonal factorization system associated to any modality, of which the…

Category Theory · Mathematics 2020-10-28 Felix Cherubini , Egbert Rijke

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

This is a survey. The main subject of this survey is the homotopical or homological nature of certain structures which appear in classical problems about groups, Lie rings and group rings. It is well known that the (generalized) dimension…

Group Theory · Mathematics 2021-11-02 Roman Mikhailov

Given a topological group G, its orbit category Orb_G has the transitive G-spaces G/H as objects and the G-equivariant maps between them as morphisms. A well known theorem of Elmendorf then states that the category of G-spaces and the…

Algebraic Topology · Mathematics 2007-05-23 Andre Henriques , David Gepner

We define a notion of Morse function and establish Morse theory-like theorems over offsets of any compact set in a Euclidean space at regular values of their distance function. Using non-smooth analysis and tools from geometric measure…

Geometric Topology · Mathematics 2025-07-28 Antoine Commaret

We introduce the category HG, whose objects are topological groupoids endowed with compatible measure theoretic data: a Haar system and a measure on the unit space. We then define and study the notion of weak-pullback in the category of…

Functional Analysis · Mathematics 2011-01-18 Aviv Censor , Daniele Grandini