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B-fields over a groupoid with involution are defined as Real graded Dixmier-Douady bundles. We use these to introduce the Real graded Brauer group which constitutes the set of twistings for Atiyah's KR-functor in the category of locally…

K-Theory and Homology · Mathematics 2011-11-01 El-kaïoum M. Moutuou

We reinterpret the residue map for the Brauer group of a smooth variety using a root stack construction and Weil restriction for algebraic stacks, and apply the result to find a geometric representative of for the residue of a Brauer class…

Algebraic Geometry · Mathematics 2018-06-22 Jakob Oesinghaus

We relate the Brauer group of a Kummer surface to the Brauer group of the corresponding abelian surface. For many pairs of elliptic curves over the rational numbers we prove that the Kummer surface attached to their product has trivial…

Algebraic Geometry · Mathematics 2010-11-09 Alexei N. Skorobogatov , Yuri G. Zarhin

We show that for complex analytic K3 surfaces any torsion class in H^2(X,O_X^*) comes from an Azumaya algebra. In other words, the Brauer group equals the cohomological Brauer group. For algebraic surfaces, such results go back to…

Algebraic Geometry · Mathematics 2007-05-23 Daniel Huybrechts , Stefan Schroeer

In this paper we give an algorithm for computing equations of Brauer-Severi varieties over perfect fields of characteristic 0. As an example we show the equations of all Brauer-Severi surfaces defined over $\mathbb{Q}$.

Number Theory · Mathematics 2020-10-06 Elisa Lorenzo García

Transcendental Brauer elements are notoriously difficult to compute. Work of Wittenberg, and later, Ieronymou, gives a method for computing 2-torsion transcendental classes on surfaces that have a genus 1 fibration with rational 2-torsion…

Algebraic Geometry · Mathematics 2012-02-29 Bianca Viray

Let ${\mathcal P}{\mathcal M}^\alpha_s$ be a moduli space of stable parabolic vector bundles of rank $n \geq 2$ and fixed determinant of degree $d$ over a compact connected Riemann surface $X$ of genus $g(X) \geq 2$. If $g(X) = 2$, then we…

Algebraic Geometry · Mathematics 2010-12-27 Indranil Biswas , Arijit Dey

We determine the decomposition matrices of the Brauer algebra over the complex field.

Representation Theory · Mathematics 2009-08-12 Paul P Martin

We introduce a version of the Brauer--Wall group for Real vector bundles of algebras (in the sense of Atiyah), and compare it to the topological analogue of the Witt group. For varieties over the reals, these invariants capture the…

Algebraic Topology · Mathematics 2019-08-01 Max Karoubi , Charles Weibel

We consider those projective bundles (or Brauer-Severi varieties) over an abelian variety that are homogeneous, i.e., invariant under translation. We describe the structure of these bundles in terms of projective representations of…

Algebraic Geometry · Mathematics 2016-01-20 Michel Brion

We suggest an effective procedure to calculate numerical invariants for rank two bundles over blown-up surfaces. We study the moduli spaces M_j of bundles on the blown-up plane splitting over the exceptional divisor as O(j)+O(-j). We use…

Algebraic Geometry · Mathematics 2007-05-23 E. Ballico , E. Gasparim

In this article we show how to compute a matrix representation and the implicit equation by means of the method developed in [Botbol: arXiv:1007.3437], using the computer algebra system Macaulay2 \cite{M2}. As it is probably the most…

Algebraic Geometry · Mathematics 2010-07-22 Nicolas Botbol

We prove an existence result for stable vector bundles with arbitrary rank on an algebraic surface, and determine the birational structure of certain moduli space of stable bundles on a rational ruled surface.

Algebraic Geometry · Mathematics 2016-09-06 Wei-ping Li , Zhenbo Qin

The paper deals with the cohomological invariants of smooth and connected linear algebraic groups over an arbitrary field. More precisely, we study degree $2$ invariants with coefficients $\mathbb{Q}/\mathbb{Z}(1)$, that is invariants…

Algebraic Geometry · Mathematics 2025-09-30 Alexandre Lourdeaux

For a prime $p$, we study subgroups of order p of the Brauer group Br(S) of a general complex polarized K3 surface of degree 2d, generalizing earlier work of van Geemen. These groups correspond to sublattices of index p of the…

Algebraic Geometry · Mathematics 2021-12-28 Kelly McKinnie , Justin Sawon , Sho Tanimoto , Anthony Várilly-Alvarado

We describe a practical algorithm for computing Brauer-Manin obstructions to the existence of rational points on hyperelliptic curves defined over number fields. This offers advantages over descent based methods in that its correctness does…

Number Theory · Mathematics 2023-05-05 Brendan Creutz , Duttatrey Nath Srivastava

This is an English translation of the author's 1989 note in Russian, published in a collection "Arithmetic and Geometry of Varieties" (V.E. Voskresenski, ed.), Kuibyshev State University, Kuibyshev, 1989, pp. 57--67. Let $X$ be be an…

Number Theory · Mathematics 2018-02-07 Yuri G. Zarhin

We describe an algorithm for computing certain characteristic numbers of surface scrolls using degenerations. As a corollary we obtain a method for computing the corresponding Gromov-Witten invariants of Grassmannians.

Algebraic Geometry · Mathematics 2007-05-23 Izzet Coskun

Let $X$ be a K3 surface defined over a number field $k$, with principal complex multiplication by a CM field $E$. We find explicit bounds, in terms of $k$ and $E$, on the size of the transcendental Brauer group…

Number Theory · Mathematics 2025-02-14 Sebastian Monnet

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