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Let A be an Azumaya algebra over a smooth projective variety X or more generally, a torsion free coherent sheaf of algebras over X whose generic fiber is a central simple algebra. We show that generically simple torsion free A-module…

Algebraic Geometry · Mathematics 2007-05-23 Norbert Hoffmann , Ulrich Stuhler

We construct an adjunction between $m$-categories internal to $(\infty,n)$-categories, called $(n,m)$-double $\infty$-categories, and filtrations $A_0\to \dots\to A_m$ where for all $i<m$, $A_i$ is a $(n+i)$-category. We show that this…

Category Theory · Mathematics 2025-03-26 Félix Loubaton

We present an elementary proof of the fact that every torsor for an affine group scheme over an algebraically closed field is trivial. This is related to the uniqueness of fibre functors on neutral tannakian categories.

Algebraic Geometry · Mathematics 2022-03-31 Michael Wibmer

Let $X$ be a smooth variety over a field $K$ with function field $K(X)$. Using the interpretation of the torsion part of the \'etale cohomology group $H_{\text{\'et}}^2(K(X), \mathbb{G}_m)$ in terms of Milnor-Quillen algebraic $K$-group…

Algebraic Geometry · Mathematics 2024-09-04 Mohammed Moutand

We develop a theory of curved A-infinity-categories around equivalences of their module categories. This allows for a uniform treatment of curved and uncurved A-infinity-categories which generalizes the classical theory of uncurved…

Algebraic Geometry · Mathematics 2015-10-16 Jeffrey Armstrong , Patrick Clarke

We use the terms $\infty$-categories and $\infty$-functors to mean the objects and morphisms in an $\infty$-cosmos: a simplicially enriched category satisfying a few axioms, reminiscent of an enriched category of fibrant objects.…

Category Theory · Mathematics 2016-06-14 Emily Riehl , Dominic Verity

It is well known that all torsors under an affine algebraic group over an algebraically closed field are trivial. We note that under suitable conditions this also holds if the the group is not necessarily of finite type. This has an…

Group Theory · Mathematics 2013-04-24 C. Deninger

In this paper we prove local-global principles for embedding of fields with involution into central simple algebras with involution over a global field. These should be of interest in study of classical groups over global fields. We deduce…

Number Theory · Mathematics 2009-07-02 Gopal Prasad , Andrei S. Rapinchuk

Let $A$ be a finite dimensional algebra (possibly with some extra structure) over an infinite field $K$ and let $r\in\mathbb{N}$. The $r$-tuples $(a_1,\dots,a_r)\in A^r$ which fail to generate $A$ are the $K$-points of a closed subvariety…

Rings and Algebras · Mathematics 2024-10-08 Omer Cantor , Uriya A. First

We consider algebras defined over a complete, local and noetherian ground ring. They are gentle algebras in case the ground ring is a field. The unbounded homotopy category of complexes of projective modules is considered. Complexes with…

Representation Theory · Mathematics 2019-10-31 Raphael Bennett-Tennenhaus

The article is a contribution to the local theory of geometric Langlands correspondence. The main result is a categorification of the isomorphism between the (extended) affine Hecke algebra, thought of as an algebra of Iwahori bi-invariant…

Representation Theory · Mathematics 2021-10-14 Roman Bezrukavnikov

We prove a localization theorem for the type A rational Cherednik algebra H_c=H_{1,c} over an algebraic closure of the finite field F_p. In the most interesting special case where the parameter c takes values in F_p, we construct an Azumaya…

Representation Theory · Mathematics 2021-11-25 Roman Bezrukavnikov , Michael Finkelberg , Victor Ginzburg

We prove a "Generic Equivalence Theorem which says that two affine morphisms $p: S \to Y$ and $q: T \to Y$ of varieties with isomorphic (closed) fibers become isomorphic under a dominant etale base change $\phi: U \to Y$. A special case is…

Representation Theory · Mathematics 2012-04-17 Hanspeter Kraft , Peter Russell

Consider a Maslov zero Lagrangian submanifold diffeomorphic to a Lie group on which an anti-symplectic involution acts by the inverse map of the group. We show that the Fukaya $A_\infty$ endomorphism algebra of such a Lagrangian is…

Symplectic Geometry · Mathematics 2020-06-16 Jake P. Solomon

Let T -> S be a finite flat morphism of degree two between regular integral schemes of dimension at most two (and with 2 invertible), having regular branch divisor D. We establish a bijection between Azumaya quaternion algebras on T and…

Algebraic Geometry · Mathematics 2012-07-18 Asher Auel , R. Parimala , V. Suresh

Let $G$ be a simply connected semisimple group over $\mathbb{C}$. We show that a certain involution of an open subset of the affine Grassmannian of $G$, defined previously by Achar and the author, corresponds to the action of the nontrivial…

Representation Theory · Mathematics 2019-06-20 Anthony Henderson

We give scheme-theoretic descriptions of the category of fibre functors on the categories of sheaves associated to the Zariski, Nisnevich, \'etale, rh, cdh, ldh, eh, qfh, and h topologies on the category of separated schemes of finite type…

Algebraic Geometry · Mathematics 2014-12-09 Ofer Gabber , Shane Kelly

In this paper we develop methods for classifying Baker-Richter-Szymik's Azumaya algebras over a commutative ring spectrum, especially in the largely inaccessible case where the ring is nonconnective. We give obstruction-theoretic tools,…

Algebraic Topology · Mathematics 2021-07-01 David Gepner , Tyler Lawson

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 develop Azumaya geometry, which is an extension of classical affine geometry to the world of Azumaya algebras, and package the information contained in all quotient stacks $[\mathrm{rep}_n R\,/\,\mathrm{PGL}_n]$ into a presheaf…

Rings and Algebras · Mathematics 2019-08-07 Jens Hemelaer , Lieven Le Bruyn