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Let $G$ be a connected simply-connected simple algebraic group over $\mathbb{C}$ and let $T$ be a maximal torus, $B\supset T$ a Borel subgroup and $K$ a maximal compact subgroup. Then, the product in the (algebraic) based loop group…

K-Theory and Homology · Mathematics 2025-10-10 Shrawan Kumar

In the present paper we introduce and study the notion of an equivariant pretheory: basic examples include equivariant Chow groups, equivariant K-theory and equivariant algebraic cobordism. To extend this set of examples we define an…

Algebraic Geometry · Mathematics 2013-02-07 Stefan Gille , Kirill Zainoulline

A group action on the input ring or category induces an action on the algebraic $K$-theory spectrum. However, a shortcoming of this naive approach to equivariant algebraic $K$-theory is, for example, that the map of spectra with $G$-action…

Algebraic Topology · Mathematics 2016-09-14 Mona Merling

Recent work of Chen He has determined through GKM methods the Borel equivariant cohomology with rational coefficients of the isotropy action on a real Grassmannian and an real oriented Grassmannian through GKM methods. In this expository…

Algebraic Topology · Mathematics 2023-11-28 Jeffrey D. Carlson

We prove a general form of the statement that the cohomology of a quotient stack can be computed by the Borel construction. It also applies to the lisse extensions of generalized cohomology theories like motivic cohomology and algebraic…

Algebraic Geometry · Mathematics 2025-09-29 Adeel A. Khan , Charanya Ravi

The goal of the present paper is the calculation of the equivariant twisted K-theory of a compact Lie group which acts on itself by conjugations, and elements of a TQFT-structure on the twisted K-groups. These results are originally due to…

K-Theory and Homology · Mathematics 2007-05-23 Ulrich Bunke , Ingo Schroeder

We study relative algebraic K-theory of admissible Zariski-Riemann spaces and prove that it is equivalent to G-theory and satisfies homotopy invariance. Moreover, we provide an example of a non-noetherian abelian category whose negative…

K-Theory and Homology · Mathematics 2024-03-06 Christian Dahlhausen

Using the Witten deformation and localization algebra techniques, we compute the $G$-equivariant $K$-homology class of the de Rham operator on a proper cocompact $G$-spin manifold, where $G$ is an almost connected Lie group. By applying a…

Operator Algebras · Mathematics 2025-08-22 Hongzhi Liu , Hang Wang , Zijing Wang , Shaocong Xiang

For an $r$-discrete Hausdorff groupoid ${\cal G}$ and an inverse semigroup $S$ of slices of ${\cal G}$ there is an isomorphism between ${\cal G}$-equivariant $KK$-theory and compatible $S$-equivariant $KK$-theory. We use it to define…

K-Theory and Homology · Mathematics 2012-11-22 Bernhard Burgstaller

We introduce a notion of morphism of CohFT algebras, based on the analogy with A-infinity morphisms. We discuss a "quantization" of the classical Kirwan morphism to a morphism of CohFT algebras from the equivariant quantum cohomology of a…

Algebraic Geometry · Mathematics 2012-12-07 Khoa Lu Nguyen , Chris Woodward , Fabian Ziltener

Using the notion of equivariant Kirwan map, as defined by Goldin, we prove that -- in the case of Hamiltonian torus actions with isolated fixed points -- Tolman and Weitsman's description of the kernel of the Kirwan map can be deduced…

Symplectic Geometry · Mathematics 2007-05-23 Lisa C. Jeffrey , Augustin-Liviu Mare

Following an outline of Rezk, we give a construction of complex-analytic $G$-equivariant elliptic cohomology for an arbitrary compact Lie group $G$ and we prove some of its fundamental properties. The construction is parametrised over the…

Algebraic Topology · Mathematics 2024-08-06 Matthew Spong

We interpret certain equivariant Kasparov groups as equivariant representable K-theory groups. We compute these groups via a classifying space and as K-theory groups of suitable sigma-C*-algebras. We also relate equivariant vector bundles…

K-Theory and Homology · Mathematics 2015-10-23 Heath Emerson , Ralf Meyer

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

The theme of this paper is to compute hermitian $K$-groups in terms of the recently developed theory of Milnor-Witt motivic cohomology. Our approach makes use of the very effective slice spectral sequence within the motivic stable homotopy…

Algebraic Geometry · Mathematics 2025-09-23 Håkon Kolderup , Oliver Röndigs , Paul Arne Østvær

Let W be a smooth complex quasiprojective variety with the action of a connected reductive group G. Adapting the stratification approach of Teleman to a microlocal context, we prove a vanishing theorem for the functor of G-invariant…

Algebraic Geometry · Mathematics 2017-02-22 Kevin McGerty , Thomas Nevins

A Theorem due to Guillemin and Sternberg about geometric quantization of Hamiltonian actions of compact Lie groups $G$ on compact Kaehler manifolds says that the dimension of the $G$-invariant subspace is equal to the Riemann-Roch number of…

alg-geom · Mathematics 2008-02-03 Eckhard Meinrenken

An important combinatorial result in equivariant cohomology and $K$-theory Schubert calculus is represented by the formulas of Billey and Graham-Willems for the localization of Schubert classes at torus fixed points. These formulas work…

Algebraic Geometry · Mathematics 2017-11-01 Cristian Lenart , Kirill Zainoulline

Freed, Hopkins and Teleman constructed an isomorphism between twisted equivariant K-theory of compact Lie group $G$ and the "Verlinde ring" of the loop group of $G$. We call this isomorphism FHT isomorphism. However, it does not hold…

K-Theory and Homology · Mathematics 2015-02-13 Doman Takata

Let G be a compact, connected Lie group, acting smoothly on a manifold M. Goresky-Kottwitz-MacPherson described a small Cartan model for the equivariant cohomology of M, quasi-isomorphic to the standard Cartan complex of equivariant…

Differential Geometry · Mathematics 2007-07-26 A. Alekseev , E. Meinrenken