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We construct uncountably many mutually nonisomorphic simple separable stably finite unital exact C$^\ast$-algebras which are not isomorphic to their opposite algebras. In particular, we prove that there are uncountably many possibilities…

Operator Algebras · Mathematics 2024-02-14 N. Christopher Phillips , Maria Grazia Viola

We define the filtrated K-theory of a C*-algebra over a finite topological space X and explain how to construct a spectral sequence that computes the bivariant Kasparov theory over X in terms of filtrated K-theory. For finite spaces with…

Operator Algebras · Mathematics 2015-10-23 Ralf Meyer , Ryszard Nest

The Isomorphism Conjecture is a conceptional approach towards a calculation of the algebraic K-theory of a group ring RG, where G is an infinite group. In this paper we prove the conjecture in dimensions n<2 for fundamental groups of closed…

Algebraic Topology · Mathematics 2007-05-23 Arthur Bartels , Tom Farrell , Lowell Jones , Holger Reich

Let Gamma be a semidirect product of the form Z^n rtimes Z/p where p is prime and the Z/p-action on Z^n is free away from the origin. We will compute the topological K-theory of the real and complex group C*-algebra of Gamma and show that…

K-Theory and Homology · Mathematics 2015-11-30 James F. Davis , Wolfgang Lueck

K-Theory for hermitian symmetric spaces of non-compact type, as developed recently by the authors, allows to put Cartan's classification into a homological perspective. We apply this method to the case of inductive limits of finite…

K-Theory and Homology · Mathematics 2016-09-23 Dennis Bohle , Wend Werner

This paper is comprised of two related parts. First we discuss which k-graph algebras have faithful gauge invariant traces, where the gauge action of $\T^k$ is the canonical one. We give a sufficient condition for the existence of such a…

Operator Algebras · Mathematics 2007-05-23 David Pask , Adam Rennie , Aidan Sims

There are many classes of nonsimple graph C*-algebras that are classified by the six-term exact sequence in K-theory. In this paper we consider the range of this invariant and determine which cyclic six-term exact sequences can be obtained…

Operator Algebras · Mathematics 2015-10-30 Søren Eilers , Takeshi Katsura , Mark Tomforde , James West

This paper addresses the isomorphism problem for the universal (nonself-adjoint) operator algebras generated by a row contraction subject to homogeneous polynomial relations. We find that two such algebras are isometrically isomorphic if…

Operator Algebras · Mathematics 2011-07-15 Kenneth R. Davidson , Christopher Ramsey , Orr Shalit

Symmetric homology is an analog of cyclic homology in which the cyclic groups are replaced by symmetric groups. The foundations for the theory of symmetric homology of algebras are developed in the context of crossed simplicial groups using…

Algebraic Topology · Mathematics 2008-07-29 Shaun Ault

Let $X/K$ be a variety over a field, and $A/K$ an abelian variety. A regular homomorphism to $A$ (in codimension $i$) induces, for every smooth geometrically connected pointed $K$-scheme $(T,t_0)$ and every cycle class $Z \in CH^i(T\times…

Algebraic Geometry · Mathematics 2025-06-23 Jeff Achter , Sebastian Casalaina-Martin , Charles Vial

We compare two approaches which use K-theory for C*-algebras to classify symmetry protected topological phases of quantum systems described in the one particle approximation. In the approach by Kellendonk, which is more abstract and more…

Operator Algebras · Mathematics 2025-12-02 Scaglione Lorenzo

A series of recent papers by Bergfalk, Lupini and Panagiotopoulus developed the foundations of a field known as `definable algebraic topology,' in which classical cohomological invariants are enriched by viewing them as groups with a Polish…

Logic · Mathematics 2025-07-21 Nicholas Meadows

We show that filtered K-theory is equivalent to a substantially smaller invariant for all real-rank-zero C*-algebras with certain primitive ideal spaces -- including the infinitely many so-called accordion spaces for which filtered K-theory…

Operator Algebras · Mathematics 2013-11-05 Sara Arklint , Rasmus Bentmann , Takeshi Katsura

Topological cyclic homology is a refinement of Connes--Tsygan's cyclic homology which was introduced by B\"okstedt--Hsiang--Madsen in 1993 as an approximation to algebraic $K$-theory. There is a trace map from algebraic $K$-theory to…

Algebraic Topology · Mathematics 2018-09-10 Thomas Nikolaus , Peter Scholze

Let $\Gamma$ be a torsion-free arithmetic group acting on its associated global symmetric space $X$. Assume that $X$ is of non-compact type and let $\Gamma$ act on the geodesic boundary $\partial X$ of $X$. Via general constructions in…

K-Theory and Homology · Mathematics 2017-09-19 Bram Mesland , Mehmet Haluk Sengun

Let H(R,q) be an affine Hecke algebra with a positive parameter function q. We are interested in the topological K-theory of H(R,q), that is, the K-theory of its C*-completion C*_r (R,q). We will prove that $K_* (C*_r (R,q))$ does not…

K-Theory and Homology · Mathematics 2018-07-25 Maarten Solleveld

Given a graph of C*-algebras, we prove a long exact sequence in KK-theory for both the maximal and the vertex-reduced fundamental C*-algebras in the presence of possibly non GNS-faithful conditional expectations. We deduce from it the…

Operator Algebras · Mathematics 2016-12-28 Fima Pierre , Germain Emmanuel

In this paper we give a complete description of K-theory groups for Cuntz-Krieger C*-algebras associated to general locally-finite (topologically connected) graphs via Bass-Hashimoto operator. Our result generalizes the one obtained by the…

Operator Algebras · Mathematics 2015-12-31 Nikolay Ivankov , Natalia Iyudu

We show existence of a natural rational structure on periodic cyclic homology, conjectured by L. Katzarkov, M. Kontsevich, T. Pantev, for several classes of dg-categories, including proper connective $\mathbb{C}$-dg-algebras and…

K-Theory and Homology · Mathematics 2021-02-03 Andrey Konovalov

We extend the stable motivic homotopy category of Voevodsky to the class of scalloped algebraic stacks, and show that it admits the formalism of Grothendieck's six operations. Objects in this category represent generalized cohomology…

Algebraic Geometry · Mathematics 2024-10-10 Adeel A. Khan , Charanya Ravi