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Stratified-algebraic vector bundles on real algebraic varieties have many desirable features of algebraic vector bundles but are more flexible. We give a characterization of the compact real algebraic varieties having the following…

Algebraic Geometry · Mathematics 2015-11-16 Wojciech Kucharz , Krzysztof Kurdyka

We construct a birational invariant for certain algebraic group actions. We use this invariant to classify linear representations of finite abelian groups up to birational equivalence, thus answering, in a special case, a question of E. B.…

Algebraic Geometry · Mathematics 2007-05-23 Zinovy Reichstein , Boris Youssin

The purpose of this paper is to lay the foundations of a theory of invariants in \'etale cohomology for smooth Artin stacks. We compute the invariants in the case of the stack of elliptic curves, and we use the theory we developed to get…

Algebraic Geometry · Mathematics 2017-07-05 Roberto Pirisi

One describes, using a detailed analysis of Atiyah--Hirzebruch spectral sequence, the tuples of cohomology classes on a compact, complex manifold, corresponding to the Chern classes of a complex vector bundle of stable rank. This…

Algebraic Geometry · Mathematics 2007-05-23 Constantin Bǎnicǎ , Mihai Putinar

We show that the Atiyah-Hirzebruch K-theory of spaces admits a canonical generalization for stratified spaces. For this we study algebraic constructions on stratified vector bundles. In particular the tangent bundle of a stratified manifold…

K-Theory and Homology · Mathematics 2007-05-23 Hans-Joachim Baues , Davide L. Ferrario

We study a new object that can be attached to an abelian variety or a complex torus: the invariant Brauer group, as recently defined by Yang Cao. Over the field of complex numbers this is an elementary abelian 2-group with an explicit upper…

Algebraic Geometry · Mathematics 2021-06-01 Martin Orr , Alexei N. Skorobogatov , Domenico Valloni , Yuri G. Zarhin

We construct and study a bicategory of super 2-line bundles over graded Lie groupoids, providing a unified framework for geometric models of twistings of (Real) K-theory. The core of our work is to exhibit a wide range of models from the…

Algebraic Topology · Mathematics 2025-02-26 Tim Lüders , Lynn Otto , Konrad Waldorf

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

The purpose of this paper is to compute determinant index bundles of certain families of Real Dirac type operators on Klein surfaces as elements in the corresponding Grothendieck group of Real line bundles in the sense of Atiyah. On a Klein…

Algebraic Geometry · Mathematics 2013-09-04 Christian Okonek , Andrei Teleman

In this paper, we study Azumaya algebras and Brauer groups in derived algebraic geometry. We establish various fundamental facts about Brauer groups in this setting, and we provide a computational tool, which we use to compute the Brauer…

Algebraic Geometry · Mathematics 2014-11-11 Benjamin Antieau , David Gepner

We construct positive-genus analogues of Welschinger's invariants for many real symplectic manifolds, including the odd-dimensional projective spaces and the renowned quintic threefold. In some cases, our invariants provide lower bounds for…

Symplectic Geometry · Mathematics 2018-02-27 Penka Georgieva , Aleksey Zinger

We define a Brauer group for differential graded algebras over differential graded graded-commutative or commutative base rings. Based on previous work we give an explicit classification of dg-fields, and compute the so-defined Brauer group…

Rings and Algebras · Mathematics 2026-05-07 Xiaoxiao Xu , Alexander Zimmermann

We develop a theory of group actions and coverings on Brauer graphs that parallels the theory of group actions and coverings of algebras. In particular, we show that any Brauer graph can be covered by a tower of coverings of Brauer graphs…

Representation Theory · Mathematics 2012-12-03 Edward L Green , Sibylle Schroll , Nicole Snashall

This paper investigates the homology of the Brauer algebras, interpreted as appropriate Tor-groups, and shows that it is closely related to the homology of the symmetric group. Our main results show that when the defining parameter of the…

Algebraic Topology · Mathematics 2023-06-13 Rachael Boyd , Richard Hepworth , Peter Patzt

We establish a theorem computing the cohomology groups of line bundles on homogeneous ind-varieties $G/B$ for diagonal ind-groups $G$. The main difficulty in proving this analog of the classical Bott-Borel-Weil theorem is in defining an…

Algebraic Geometry · Mathematics 2009-11-11 Ivan Dimitrov , Ivan Penkov

We present an algorithm to compute the Brauer group of involution surface bundles over rational surfaces.

Algebraic Geometry · Mathematics 2018-09-17 Andrew Kresch , Yuri Tschinkel

We investigate the Brauer group of the ring $\mathcal{O}(S)$ of holomorphic functions on a finite-dimensional Stein space S. We provide a purely topological computation of this group and deduce a comparison theorem between the \'etale…

Algebraic Geometry · Mathematics 2026-02-25 Olivier Benoist , James Hotchkiss

We construct connections and characteristic forms for principal bundles over groupoids and stacks in the differentiable, holomorphic and algebraic category using Atiyah sequences associated to transversal tangential distributions.

Algebraic Geometry · Mathematics 2013-11-27 Indranil Biswas , Frank Neumann

We study the Brauer groups of regular conic bundles over elliptic curves defined over a number field $k$. We explicitly compute the Brauer group of the conic bundle when the singular fibres lie above $k$-points that are divisible by $2$ in…

Algebraic Geometry · Mathematics 2025-09-22 Abdulmuhsin Alfaraj

Let $A$ be an abelian variety over a field finitely generated over $\mathbb{Q}$. We show that the finiteness of the $\ell$-primary torsion subgroup of the higher Brauer group is a sufficient criterion for the Tate conjecture to hold.…

Algebraic Geometry · Mathematics 2016-06-27 Thomas Jahn