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We use equivariant methods to establish basic properties of orbifold K-theory. We introduce the notion of twisted orbifold K-theory in the presence of discrete torsion, and show how it can be explicitly computed for global quotients.

Algebraic Topology · Mathematics 2009-11-07 Alejandro Adem , Yongbin Ruan

We compute the equivariant complex K-theory ring of a cohomogeneity-one action of a compact Lie group at the level of generators and relations and derive a characterization of K-theoretic equivariant formality for these actions. Less…

Algebraic Topology · Mathematics 2022-03-15 Jeffrey D. Carlson

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 apply results of Harada, Holm and Henriques to prove that the Atiyah-Segal equivariant complex $K$-theory ring of a divisive weighted projective space (which is singular for nontrivial weights) is isomorphic to the ring of integral…

Algebraic Topology · Mathematics 2015-02-10 Megumi Harada , Tara S. Holm , Nigel Ray , Gareth Williams

A smooth GKM stack is a smooth Deligne-Mumford stack equipped with an action of an algebraic torus $T$, with only finitely many zero-dimensional and one-dimensional orbits. (i) We define the stacky GKM graph of a smooth GKM stack, under the…

Algebraic Geometry · Mathematics 2021-03-15 Chiu-Chu Melissa Liu , Artan Sheshmani

We consider groups G which have a cocompact, 3-manifold model for the classifying space \underline{E}G. We provide an algorithm for computing the rationalized equivariant K-homology of \underline{E}G. Under the additional hypothesis that…

K-Theory and Homology · Mathematics 2013-04-30 Jean-François Lafont , Ivonne J. Ortiz , Rubén J. Sánchez-García

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

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

Recent advances in computational techniques for $K$-theory allow us to describe the $K$-theory of toric varieties in terms of the $K$-theory of fields and simple cohomological data.

K-Theory and Homology · Mathematics 2011-08-03 Guillermo Cortiñas , Christian Haesemeyer , Mark E. Walker , Charles Weibel

We study equivariant coarse homology theories through an axiomatic framework. To this end we introduce the category of equivariant bornological coarse spaces and construct the universal equivariant coarse homology theory with values in the…

K-Theory and Homology · Mathematics 2021-05-28 Ulrich Bunke , Alexander Engel , Daniel Kasprowski , Christoph Winges

Let G be a finite group acting on a finite dimensional real vector space V. We denote by P(V) the projective space associated to V. In this paper we compute in a very explicit way the rank of the equivariant complex K-theory of V and P(V),…

K-Theory and Homology · Mathematics 2007-05-23 Max Karoubi

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

In this paper we define twisted equivariant K-theory for actions of Lie groupoids. For a Bredon-compatible Lie groupoid, this defines a periodic cohomology theory on the category of finite CW-complexes with equivariant stable projective…

Algebraic Topology · Mathematics 2011-05-18 Jose Cantarero

We define quantum equivariant K-theory of Nakajima quiver varieties. We discuss type A in detail as well as its connections with quantum XXZ spin chains and trigonometric Ruijsenaars-Schneider models. Finally we study a limit which produces…

Algebraic Geometry · Mathematics 2021-09-28 Peter Koroteev , Petr P. Pushkar , Andrey Smirnov , Anton M. Zeitlin

Let $E$ be an elliptic curve defined over $\mathbb{Q}$, and let $K$ be a number field of degree four that is Galois over $\mathbb{Q}$. The goal of this article is to classify the different isomorphism types of $E(K)_{\text{tors}}$.

Number Theory · Mathematics 2015-11-05 Michael Chou

We describe the equivariant cobordism ring of smooth toric varieties. This equivariant description is used to compute the ordinary cobordism ring of such varieties.

Algebraic Geometry · Mathematics 2010-11-03 Amalendu Krishna , V. Uma

The {\it torus manifolds} have been defined and studied by M. Masuda and T. Panov (arXiv:math.AT/0306100) who in particular describe its cohomology ring structure. In this note we shall describe the topological $K$-ring of a class of torus…

Algebraic Topology · Mathematics 2007-05-23 V. Uma

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 give a presentation for the (integral) torus-equivariant Chow ring of the quot scheme, a smooth compactification of the space of rational curves of degree d in the Grassmannian. For this presentation, we refine Evain's extension of the…

Algebraic Geometry · Mathematics 2010-03-29 Tom Braden , Linda Chen , Frank Sottile

We present the fundamental properties of the K-theory groups of complex vector bundles endowed with actions of magnetic groups. In this work we show that the magnetic equivariant K-theory groups define an equivariant cohomology theory, we…

K-Theory and Homology · Mathematics 2025-05-09 Higinio Serrano , Bernardo Uribe , Miguel A. Xicoténcatl