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In topology there is a theorem of Atiyah, concerning K-theory of classifying space of connected compact Lie group. We consider an algebraic analogue of this theorem. We prove that for a split reductive algebraic group G over a field there…

K-Theory and Homology · Mathematics 2011-11-22 Alisa Knizel , Alexander Neshitov

We motivate and survey the theory of BPS invariants of categories and BPS cohomology of stacks, indicating applications in enumerative geometry and representation theory, as well as recent advances.

Algebraic Geometry · Mathematics 2026-01-14 Ben Davison

We construct decompositions of: (1) the cohomology of smooth stacks, (2) the Borel--Moore homology of $0$-shifted symplectic stacks, and (3) the vanishing cycle cohomology of $(-1)$-shifted symplectic stacks, assuming a good moduli space…

Algebraic Geometry · Mathematics 2025-06-03 Chenjing Bu , Ben Davison , Andrés Ibáñez Núñez , Tasuki Kinjo , Tudor Pădurariu

We introduce a Hopf algebroid associated to a proper Lie group action on a smooth manifold. We prove that the cyclic cohomology of this Hopf algebroid is equal to the de Rham cohomology of invariant differential forms. When the action is…

Differential Geometry · Mathematics 2010-02-25 Xiang Tang , Yi-Jun Yao , Weiping Zhang

We introduce a new cohomology theory for stacks called elliptic Hochschild homology, prove some fundamental properties and compute it in some classes of examples. We then introduce its periodic cyclic version and show that, over the complex…

Algebraic Geometry · Mathematics 2023-09-18 Nicolò Sibilla , Paolo Tomasini

We prove that if $G$ is a finite flat group scheme of $p$ power rank over a perfect field of characteristic $p$, then the second crystalline cohomology of its classifying stack $H^2_{crys}(BG)$ recovers the Dieudonn\'e module of $G$. We…

Algebraic Geometry · Mathematics 2023-06-22 Shubhodip Mondal

Lecture notes. Introduction to the cohomology of algebras, Lie algebras, Lie bialgebras and quantum groups. Contains a new derivation of the classification of classical r-matrices in terms of deformation cohomology, and a calculation of the…

q-alg · Mathematics 2014-05-27 Christian Fronsdal

Let G be a compact, connected and simply connected Lie group, and {\Omega}G the space of the loops in G based at the identity. This note shows a way to compute the cohomology of the total space of a principal {\Omega}G-bundle over a…

Algebraic Topology · Mathematics 2013-09-26 Samuel Tinguely

Let $G$ be the classical group, and let Hom$(\mathbb{Z}^m,G)$ denote the space of commuting $m$-tuples in $G$. Baird proved that the cohomology of Hom$(\mathbb{Z}^m,G)$ is identified with a certain ring of invariants of the Weyl group of…

Algebraic Topology · Mathematics 2020-10-19 Masahiro Takeda

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

Higher order cohomology of arithmetic groups is expressed in terms of (g,K)-cohomology. Generalizing results of Borel, it is shown that the latter can be computed using functions of (uniform) moderate growth. A higher order versions of…

Number Theory · Mathematics 2008-05-16 Anton Deitmar

We develop a framework that systematically casts the solvability and uniqueness conditions of linearized geometric boundary-value problems into cohomological terms. The theory is designed to be applicable without assumptions on the…

Differential Geometry · Mathematics 2026-03-16 Roee Leder

Bredon cohomology is a cohomology theory that applies to topological spaces equipped with the group actions. For any group G, given a real linear representation V , the configuration space of V has a natural diagonal G-action. In the paper…

Algebraic Topology · Mathematics 2022-04-20 Qiaofeng Zhu

We consider families of reductive complexes related by level-raising operators and originating from an associative algebra. In the main theorem it is shown that the multiple cohomology of that complexes is given by the factor space of…

Functional Analysis · Mathematics 2024-08-13 A. Zuevsky

We prove a Hodge-type decomposition for the de-Rham cohomology of $ p$-adically uniformized varieties by the product of Drinfeld's symmetric spaces. It is based on work of Schneider, Stuhler, Iovita and Spiess on the cohomology of…

Algebraic Geometry · Mathematics 2018-11-06 Yufan Luo

Let G be a reductive algebraic group over a field of prime characteristic. One can associate to G (or subgroups thereof) its Lie algebra, its Frobenius kernels, and the finite Chevalley group of points over a finite field. The…

Representation Theory · Mathematics 2023-07-10 Christopher P. Bendel

We show that the vector bundle on the moduli stack $M_\mathrm{ell}$ of elliptic curves associated to the $2$-cell complex $C\nu$ is isomorphic to the de Rham cohomology sheaf $\mathrm{H}^1_\mathrm{dR}(\mathcal{E}/M_\mathrm{ell})$ of the…

Algebraic Topology · Mathematics 2019-12-06 Sanath K. Devalapurkar

We construct Hodge filtered cohomology groups for complex manifolds that combine the topological information of generalized cohomology theories with geometric data of Hodge filtered holomorphic forms. This theory provides a natural…

Algebraic Topology · Mathematics 2017-05-17 Michael J. Hopkins , Gereon Quick

We give a formula comparing the E-series of the moduli stacks of rank 2 degree 0 semistable Higgs bundles in genus $g \geq 2$ to intersection E-polynomials of its coarse moduli space. A parellel formula holds in various 2-Calabi-Yau…

Algebraic Geometry · Mathematics 2023-10-05 Sebastian Schlegel Mejia

For any type of fundamental groupoid scheme, we construct an algebraic cohomology theory for varieties with coefficients in the base field. This is a minor variant of \'etale cohomology, involving neither de Rham complexes nor…

Algebraic Geometry · Mathematics 2026-02-16 Hyuk Jun Kweon