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A parametrized spectrum E is a family of spectra E_x continuously parametrized by the points x of a topological space X. We take the point of view that a parametrized spectrum is a bundle-theoretic geometric object. When R is a ring…

Algebraic Topology · Mathematics 2017-02-28 John Lind

This is half an overview article since what we describe here is essentially known. We describe $KK$-theory by generators and relations in a formal sum of formal products of $*$-homomorphisms and some synthetical morphisms. What comes out is…

K-Theory and Homology · Mathematics 2016-09-02 Bernhard Burgstaller

We present a quick approach to computing the $K$-theory of the category of locally compact modules over any order in a semisimple $\mathbb{Q}$-algebra. We obtain the $K$-theory by first quotienting out the compact modules and subsequently…

K-Theory and Homology · Mathematics 2020-06-22 Oliver Braunling , Ruben Henrard , Adam-Christiaan van Roosmalen

The construction of topological index maps for equivariant families of Dirac operators requires factoring a general smooth map through maps of a very simple type: zero sections of vector bundles, open embeddings, and vector bundle…

K-Theory and Homology · Mathematics 2012-06-29 Ralf Meyer , Heath Emerson

In this paper we provide descriptions of the Whitehead groups with coefficients in a ring of the Hilbert modular group and its reduced version, as well as for the topological K-theory of $C^*$-algebras, after tensoring with $\mathbb{Q}$, by…

K-Theory and Homology · Mathematics 2017-06-16 Luis Jorge Sánchez Saldaña , Mario Velásquez

We study index pairings for crossed-product $C^*$-algebras arising from minimal actions on the Cantor set. We utilize Putnam's orbit-breaking AF-subalgebras and embeddings to show we can compute any index pairing for Cantor minimal system…

Operator Algebras · Mathematics 2025-06-02 Levi Lorenzo

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

By considering the general properties of approximate units in differentiable algebras, we are able to present a unified approach to characterising completeness of spectral metric spaces, existence of connections on modules, and the lifting…

Operator Algebras · Mathematics 2016-10-24 Bram Mesland , Adam Rennie

We prove a localization formula in equivariant algebraic $K$-theory for an arbitrary complex algebraic group acting with finite stabilizer on a smooth algebraic space. This extends to non-diagonalizable groups the localization formulas H.A.…

Algebraic Geometry · Mathematics 2007-05-23 Dan Edidin , William Graham

We develop important properties of the KK-functor on the basis of split exactness. In particular we discuss two slightly different short proofs for the existence of the Kasparov product and its associativity. We use the approach with…

Operator Algebras · Mathematics 2025-08-21 Joachim Cuntz

Let $G$ be a connected, linear, real reductive Lie group with compact centre. Let $K<G$ be maximal compact. For a tempered representation $\pi$ of $G$, we realise the restriction $\pi|_K$ as the $K$-equivariant index of a Dirac operator on…

Representation Theory · Mathematics 2018-05-07 Peter Hochs , Yanli Song , Shilin Yu

The multipullback quantization of complex projective spaces lacks the naive quantum CW-complex structure because the quantization of an embedding of the $n$-skeleton into the $(n+1)$-skeleton does not exist. To overcome this difficulty, we…

K-Theory and Homology · Mathematics 2022-01-03 Francesco D'Andrea , Piotr M. Hajac , Tomasz Maszczyk , Albert Sheu , Bartosz Zielinski

On a compact Lie group $G$, we consider the reproducing kernel Hilbert space $\mathcal{H}_K$ associated with the integral kernel $K$ of a left-invariant, positive, symmetric, trace class integral operator on $L^2(G)$. We present lower and…

Functional Analysis · Mathematics 2026-02-03 Zhirayr Avetisyan , Michael Ruzhansky , Karina Gonzalez

Let A denote the C*-algebra of bounded operators on L^2(RxS^1) generated by: (a) multiplications by smooth functions on S^1; (b) multiplications by continuous functions on the two point compactification of R; (c) multiplications by…

Operator Algebras · Mathematics 2009-05-20 Patricia Hess

For any Lie groupoid we construct an analytic index morphism taking values in a modified $K-theory$ group which involves the convolution algebra of compactly supported smooth functions over the groupoid. The construction is performed by…

K-Theory and Homology · Mathematics 2008-03-17 Paulo Carrillo Rouse

Let G be a locally compact, Hausdorff groupoid in which s is a local homeomorphism and the unit space is totally disconnected. Assume there is a continuous cocycle c from G into a discrete group $\Gamma$. We show that the collection A(G) of…

Rings and Algebras · Mathematics 2012-02-07 Lisa Orloff Clark , Cynthia Farthing , Aidan Sims , Mark Tomforde

We address the general classification problem of all stable associative product structures in the complex cobordism theory. We show how to reduce this problem to the algebraic one in terms of the Hopf algebra $S$ (the Landweber-Novikov…

Algebraic Topology · Mathematics 2007-05-23 B. Botvinnik , V. Buchstaber , S. Novikov , S. Yuzvinsky

We give a brief review of the cohomological Hall algebra CoHA $\mathcal{H}$ and the K-theoretical Hall algebra KHA $\mathcal{R}$ associated to quivers. In the case of symmetric quivers, we show that there exists a homomorphism of algebras…

Representation Theory · Mathematics 2022-07-26 Valery Lunts , Špela Špenko , Michel Van den Bergh

We introduce the local and global indices of Dirac operators for the rational Cherednik algebra $\mathsf{H}_{t,c}(G,\mathfrak{h})$, where $G$ is a complex reflection group acting on a finite-dimensional vector space $\mathfrak{h}$. We…

Representation Theory · Mathematics 2017-10-19 Dan Ciubotaru , Marcelo De Martino

We construct the coarse index class with support condition (as an element of coarse $K$-homology) of an equivariant Dirac operator on a complete Riemannian manifold endowed with a proper, isometric action of a group. We further show a…

Differential Geometry · Mathematics 2025-05-14 Ulrich Bunke , Alexander Engel
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