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For T an abelian compact Lie group, we give a description of T-equivariant K-theory with complex coefficients in terms of equivariant cohomology. In the appendix we give applications of this by extending results of Chang-Skjelbred and…

Algebraic Topology · Mathematics 2009-03-10 Ioanid Rosu , Allen Knutson

We introduce twisted K-theoretic Gromov-Witten invariants - in the frameworks of both "ordinary" and permutation-equivariant K-theoretic GW theory defined recently by Givental. We focus on the case when the twisting is given by the Euler…

Algebraic Geometry · Mathematics 2016-06-03 Valentin Tonita

In this paper we give a geometric construction of the Borel equivariant (co)homology for spaces with a $G$-action, where $G$ is a compact Lie group with the property that the adjoint representation is orientable. A nice feature of these…

Algebraic Topology · Mathematics 2014-01-10 Haggai Tene

In joint work with M. Hopkins and C. Teleman we find a new description of the Verlinde algebra associated to a compact Lie group. In this expository account we describe twisted K-theory, prove the theorem for the group SU(2), and motivate…

Representation Theory · Mathematics 2007-05-23 Daniel S. Freed

We investigate the K-theory of twisted higher-rank-graph algebras by adapting parts of Elliott's computation of the K-theory of the rotation algebras. We show that each 2-cocycle on a higher-rank graph taking values in an abelian group…

Operator Algebras · Mathematics 2012-11-08 Alex Kumjian , David Pask , Aidan Sims

Twisted K-theory on a manifold X, with twisting in the 3rd integral cohomology, is dis- cussed in the case when X is a product of a circle T and a manifold M. The twist is assumed to be decomposable as a cup product of the basic integral…

K-Theory and Homology · Mathematics 2014-03-19 Antti J. Harju , Jouko Mickelsson

Twisted K-theory has received much attention recently in both mathematics and physics. We describe some models of twisted K-theory, both topological and geometric. Then we state a theorem which relates representations of loop groups to…

Algebraic Topology · Mathematics 2007-05-23 Daniel S. Freed

We compute the convolution product on the equivariant K-groups of the cyclic quiver variety. We get a q-analogue of double-loop algebras, closely related to the toroidal quantum groups previously studied by the authors. We also give a…

Algebraic Geometry · Mathematics 2007-05-23 Michela Varagnolo , Eric Vasserot

We give a construction of cyclic cocycles on convolution algebras twisted by gerbes over discrete translation groupoids. For proper \'etale groupoids, Tu and Xu provide a map between the periodic cyclic cohomology of a gerbe-twisted…

Quantum Algebra · Mathematics 2015-05-27 Eitan Angel

We construct differential equivariant K-theory of representable smooth orbifolds as a ring valued functor with the usual properties of a differential extension of a cohomology theory. For proper submersions (with smooth fibres) we construct…

K-Theory and Homology · Mathematics 2015-07-16 Ulrich Bunke , Thomas Schick

We consider twisted equivariant K--theory for actions of a compact Lie group $G$ on a space $X$ where all the isotropy subgroups are connected and of maximal rank. We show that the associated rational spectral sequence \`a la Segal has a…

Algebraic Topology · Mathematics 2019-10-01 Alejandro Adem , José Cantarero , José Manuel Gómez

Let G be a discrete group. We give methods to compute for a generalized (co-)homology theory its values on the Borel construction (EG x X)/G of a proper G-CW-complex X satisfying certain finiteness conditions. In particular we give formulas…

K-Theory and Homology · Mathematics 2012-01-24 Michael Joachim , Wolfgang Lueck

We introduce a twisted version of $K$-theory with coefficients in a $C^*$-algebra $A$, where the twist is given by a new kind of gerbe, which we call Morita bundle gerbe. We use the description of twisted $K$-theory in the torsion case by…

K-Theory and Homology · Mathematics 2011-03-22 Ulrich Pennig

Inertia orbifolds homotopy-quotiented by rotation of geometric loops play a fundamental role not only in ordinary cyclic cohomology, but more recently in constructions of equivariant Tate-elliptic cohomology and generally of transchromatic…

Algebraic Topology · Mathematics 2024-02-28 Hisham Sati , Urs Schreiber

We present a decomposition of rational twisted $G$-equivariant K-theory, $G$ a finite group, into cyclic group equivariant K-theory groups of fixed point spaces. This generalises the untwisted decomposition by Atiyah and Segal as well as…

K-Theory and Homology · Mathematics 2023-12-22 Tom Dove , Thomas Schick , Mario Velásquez

For $G$ a finite group, we show that functions on fields for the 2-dimensional supersymmetric sigma model with background $G$-symmetry determine cocycles for complex analytic $G$-equivariant elliptic cohomology. Similar structures in…

Algebraic Topology · Mathematics 2020-10-13 Daniel Berwick-Evans

The interplay between equivariant stable homotopy theory and spectral algebraic geometry is used to construct a derived Tate curve over $\mathrm{KU}((q))$, a lift of the classical elliptic curve of Tate over $\mathbf{Z}((q))$. Applications…

Algebraic Topology · Mathematics 2025-03-07 Jack Morgan Davies , Sil Linskens

Let $G$ be a connected semisimple Lie group with its maximal compact subgroup $K$ being simply-connected. We show that the twisted equivariant $KK$-theory $KK^{\bullet}_{G}(G/K, \tau_G^G)$ of $G$ has a ring structure induced from the…

K-Theory and Homology · Mathematics 2021-06-30 Chi-Kwong Fok , Varghese Mathai

Generalizing a construction of Wolfgang L\"uck and Bob Oliver, we define a good equivariant cohomology theory on the category of proper G-CW complexes when G is an arbitrary Lie group (possibly non-compact). This is done by constructing an…

Algebraic Topology · Mathematics 2010-11-02 Clément de Seguins Pazzis

We show how general principles of symmetry in quantum mechanics lead to twisted notions of a group representation. This framework generalizes both the classical 3-fold way of real/complex/quaternionic representations as well as a…

High Energy Physics - Theory · Physics 2015-06-11 Daniel S. Freed , Gregory W. Moore