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In this paper we propose an approach to homotopical algebra where the basic ingredient is a category with two classes of distinguished morphisms: strong and weak equivalences. These data determine the cofibrant objects by an extension…

Algebraic Topology · Mathematics 2008-09-18 F. Guillen Santos , V. Navarro , P. Pascual , Agusti Roig

Classification questions are often about understanding components of a category. It is much more desirable however to be able to understand the entire homotopy type of this category and not just the set of its components. In this paper we…

Algebraic Topology · Mathematics 2012-06-21 Martin Blomgren , Wojciech Chacholski

We define a homotopy relation between arrows of a category with weak equivalences, and give a condition under which the quotient by the homotopy relation yields the homotopy category. In the case of the fibrant-cofibrant objects of a model…

Category Theory · Mathematics 2018-04-13 Martin Szyld

Let G be a finite group. We systematically exploit general homological methods in order to reduce the computation of G-equivariant KK-theory to topological equivariant K-theory. The key observation is that the functor assigning to a…

Operator Algebras · Mathematics 2016-05-11 Ivo Dell'Ambrogio

This survey article on relative homological algebra in bivariant K-thoery is mainly intended for readers with a background knowledge in triangulated categories. We briefly recall the general theory of relative homological algebra in…

Operator Algebras · Mathematics 2023-03-03 George Nadareishvili

In the rational cohomology of a 1-connected space a structure of $C_{\infty}$-algebra is constructed and it is shown that this object determines the rational homotopy type

Algebraic Topology · Mathematics 2008-11-12 Tornike Kadeishvili

The category of modules over the endomorphism algebra of a rigid object in a Hom-finite triangulated category C has been given two different descriptions: On the one hand, as shown by Osamu Iyama and Yuji Yoshino, it is equivalent to an…

Representation Theory · Mathematics 2014-12-24 Yann Palu

We prove that AF-embeddability is a homotopy invariant in the class of separable exact $C^*$-algebras. This work was inspired by Spielberg's work on homotopy invariance of AF-embeddability and Dadarlat's serial works on AF-embeddability of…

Operator Algebras · Mathematics 2007-05-23 Narutaka Ozawa

We prove that all eight KO groups for a real C*-algebra can be constructed from homotopy classes of unitary matrices that respect a variety of symmetries. In this manifestation of the KO groups, all eight boundary maps in the 24-term exact…

Operator Algebras · Mathematics 2019-10-22 Jeffrey L. Boersema , Terry A. Loring

We study fibred spaces with fibres in a structure category $\V$ and we show that cellular approximation, Blakers--Massey theorem, Whitehead theorems, obstruction theory, Hurewicz homomorphism, Wall finiteness obstruction, and Whitehead…

Algebraic Topology · Mathematics 2007-05-23 Hans-Joachim Baues , Davide L. Ferrario

A universal category-theoretical characterization of groupoid equivariant $KK^G$-theory for ${\mathbb{Z}}_2$-graded $C^*$-algebras is established, by observing the ``$KK$-axiom'' that for each $[s,{\cal E} \oplus B, \mathbb{F}] \in…

K-Theory and Homology · Mathematics 2026-04-07 Bernhard Burgstaller

We associate to each unital $C^*$-algebra $A$ a geometric object---a diagram of topological spaces representing quotient spaces of the noncommutative space underlying $A$---meant to serve the role of a generalized Gel'fand spectrum. After…

Operator Algebras · Mathematics 2014-08-07 Nadish de Silva

Lie $n$-algebras are the $L_\infty$ analogs of chain Lie algebras from rational homotopy theory. Henriques showed that finite type Lie $n$-algebras can be integrated to produce certain simplicial Banach manifolds, known as Lie…

Algebraic Topology · Mathematics 2020-06-03 Christopher L. Rogers

We study the E-theory group $E_{[0,1]}(A,B)$ for a class of C*-algebras over the unit interval with finitely many singular points, called elementary $C[0,1]$-algebras. We use results on E-theory over non-Hausdorff spaces to describe…

Operator Algebras · Mathematics 2013-12-17 M. Dadarlat , P. Vaidyanathan

In this work we construct a C*-algebra from an injective endomorphisms of some group G, allowing the endomorphism to have infinite cokernel. We generalize results obtained by I. Hirshberg and also by J. Cuntz and A. Vershik. In good cases…

Functional Analysis · Mathematics 2018-03-13 Felipe Vieira

We define united K-theory for real C*-algebras, generalizing Bousfield's topological united K-theory. United K-theory incorporates three functors -- real K-theory, complex K-theory, and self-conjugate K-theory -- and the natural…

Operator Algebras · Mathematics 2007-05-23 Jeffrey L. Boersema

We propose a simplified definition of Quillen's fibration sequences in a pointed model category that fully captures the theory, although it is completely independent of the concept of action. This advantage arises from the understanding…

Algebraic Topology · Mathematics 2021-09-28 Alisa Govzmann , Damjan Pištalo , Norbert Poncin

This paper investigates the $\mathrm{K}$-theory of twisted groupoid $\mathrm{C}^*$-algebras. It is shown that a homotopy of twists on an ample groupoid satisfying the Baum-Connes conjecture with coefficients gives rise to an isomorphism…

Operator Algebras · Mathematics 2019-04-25 Christian Bönicke

Locally trivial bundles of $C^*$-algebras with fibre $D \otimes \mathcal{K}$ for a strongly self-absorbing $C^*$-algebra $D$ over a finite CW-complex $X$ form a group $E^1_D(X)$ that is the first group of a cohomology theory $E^*_D(X)$. In…

Operator Algebras · Mathematics 2026-01-08 Marius Dadarlat , James E. McClure , Ulrich Pennig

Category theory provides a means through which many far-ranging fields of mathematics can be related by their similar structure. In a paper by Robinson [2], this interconnectivity afforded by categorical perspectives allowed for the…

Algebraic Topology · Mathematics 2020-12-03 Karthik Boyareddygari
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