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We study spherical Schubert varieties in the affine Grassmannian. These Schubert varieties have a natural conjectural modular description due to Finkelberg-Mirkovi\'c. This modular description is easily seen to be set-theoretically correct,…

Representation Theory · Mathematics 2016-04-04 Joel Kamnitzer , Dinakar Muthiah , Alex Weekes

We define and study a relative perverse $t$-structure associated with any finitely presented morphism of schemes $f: X\to S$, with relative perversity equivalent to perversity of the restrictions to all geometric fibres of $f$. The…

Algebraic Geometry · Mathematics 2023-05-11 David Hansen , Peter Scholze

The category of perverse sheaves on the affine Grassmannian of a complex reductive group $G$ gives a canonical geometric construction of the split form of the Langlands dual group $\check G_\bZ$ over the integers. Given a field $k$, we give…

Representation Theory · Mathematics 2008-11-18 Vivek Dhand

The goal of this paper is to construct a category of motivic "sheaves" on an algebraic variety defined over a subfield of C, using Nori's method. This categoryis abelian and it possesses faithful exact realization functors to the…

Algebraic Geometry · Mathematics 2012-10-11 Donu Arapura

We consider the construction of refined Chern-Simons torus knot invariants by M. Aganagic and S. Shakirov from the DAHA viewpoint of I. Cherednik. We give a proof of Cherednik's conjecture on the stabilization of superpolynomials, and then…

Representation Theory · Mathematics 2015-08-13 Eugene Gorsky , Andrei Neguţ

In this paper we construct an abelian category of "mixed perverse sheaves" attached to any realization of a Coxeter group, in terms of the associated Elias-Williamson diagrammatic category. This construction extends previous work of the…

Representation Theory · Mathematics 2018-07-19 Pramod N. Achar , Simon Riche , Cristian Vay

The Riemann-Hilbert correspondence embeds the triangulated category of (not necessarily regular) holonomic D-modules into that of $\mathbb R$-constructible enhanced ind-sheaves. The source category has a standard t-structure. Here, we…

Algebraic Geometry · Mathematics 2019-07-25 Andrea D'Agnolo , Masaki Kashiwara

The goal of this work is to construct a perverse t-structure on the infinity-category of l-adic LG-equivariant sheaves on the loop Lie algebra Lg and to show that the affine Grothendieck-Springer sheaf S is perverse. Moreover, S is an…

Algebraic Geometry · Mathematics 2022-09-21 Alexis Bouthier , David Kazhdan , Yakov Varshavsky

We consider the category of perverse sheaves on a complex vector space smooth with respect to a stratification given by an arrangement of hyperplanes with real equations. As shown in an earlier wotk of two of the authors, this category can…

Algebraic Topology · Mathematics 2022-06-28 Michael Finkelberg , Mikhail Kapranov , Vadim Schechtman

We prove an isomorphism for simple perverse sheaves on the affine Grassmannian of a connected reductive algebraic group that is a geometric counterpart (in light of the Finkelberg-Mirkovi\'c conjecture) of the Steinberg tensor product…

Representation Theory · Mathematics 2022-02-17 Pramod N. Achar , Simon Riche

We construct an obstruction theory for relative Hilbert schemes in the sense of Behrend-Fantechi and compute it explicitly for relative Hilbert schemes of divisors on smooth projective varieties. In the special case of curves on a surface…

Algebraic Geometry · Mathematics 2007-05-23 M. Duerr , A. Kabanov , Ch. Okonek

The invariant Hilbert schemes considered in \cite{BC1} were proved to be affine spaces. The proof relied on the classification of strict wonderful varieties. We obtain in the present article a classification-free proof of the affinity of…

Algebraic Geometry · Mathematics 2009-07-16 Stéphanie Cupit-Foutou

The aim of this paper is to identify a certain tensor category of perverse sheaves on the real loop Grassmannian of a real form $G_{\mathbb R}$ of a connected reductive complex algebraic group $G$ with the category of finite-dimensional…

Algebraic Geometry · Mathematics 2007-05-23 David Nadler

We describe the (bigraded) Hochschild cohomology of graded gentle algebras along with the Gerstenhaber bracket and cup product. In particular, this yields a description of the Hochschild cohomology of partially wrapped Fukaya categories of…

Representation Theory · Mathematics 2026-01-12 Sebastian Opper

In this paper we provide a "combinatorial" description of the category of tilting perverse sheaves on the affine flag variety of a reductive algebraic group, and its free-monodromic variant, with coefficients in a field of positive…

Representation Theory · Mathematics 2024-07-08 Roman Bezrukavnikov , Simon Riche

We introduce a new way to encode semicyclic structures using a stack of broken cycles. (We also prove an analogue for paracyclic structures.) This was motivated not only by higher algebra but also by Fukaya-categorical considerations. We…

Algebraic Topology · Mathematics 2019-07-09 Hiro Lee Tanaka

In this paper we suggest a new general formalism for studying the invariants of polyhedra and manifolds comming from the theory of von Neumann algebras. First, we examine generality in which one may apply the construction of the extended…

dg-ga · Mathematics 2008-02-03 Michael Farber

Inspired by symplectic geometry and a microlocal characterizations of perverse (constructible) sheaves we consider an alternative definition of perverse coherent sheaves. We show that a coherent sheaf is perverse if and only if…

Algebraic Geometry · Mathematics 2015-09-30 Clemens Koppensteiner

We define a quantum analogue of the Grothendieck ring of finite dimensional modules of a quantum affine algebra of simply laced type. The construction is based on perverse sheaves on a variety related to quivers. We get also a new geometric…

Quantum Algebra · Mathematics 2007-05-23 Michela Varagnolo , Eric Vasserot

Bezrukavnikov (later together with Arinkin) recovered the work of Deligne defining perverse $t$-structures for the derived category of coherent sheaves on a projective variety. In this text we prove that these $t$-structures can be obtained…

Representation Theory · Mathematics 2013-08-08 Jorge Vitoria