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It is usually not straightforward to work with the category of perverse sheaves on a variety using only its definition as a heart of a $t$-structure. In this paper, the category of perverse sheaves on a smooth toric variety with its orbit…

Algebraic Geometry · Mathematics 2024-12-30 Sergey Guminov

This paper is an introduction to the use of perverse sheaves with positive characteristic coefficients in modular representation theory. In the first part, we survey results relating singularities in finite and affine Schubert varieties and…

Representation Theory · Mathematics 2014-10-07 Daniel Juteau , Carl Mautner , Geordie Williamson

We develop a "Soergel theory" for Bruhat-constructible perverse sheaves on the flag variety $G/B$ of a complex reductive group $G$, with coefficients in an arbitrary field $\Bbbk$. Namely, we describe the endomorphisms of the projective…

Representation Theory · Mathematics 2020-02-19 Roman Bezrukavnikov , Simon Riche

Let $X$ be a topologically stratified space, $p$ be any perversity on $X$, and $k$ be a field. We show that the category of $p$-perverse sheaves on $X$, constructible with respect to the stratification and with coefficients in $k$, is…

Representation Theory · Mathematics 2020-07-08 Alessio Cipriani , Jon Woolf

This paper gives an explicit computation of the category of constructible sheaves on a toric variety (with respect to the stratification by torus orbits). Over the complex numbers, this simplifies a description due to Braden and Lunts. The…

Algebraic Geometry · Mathematics 2024-10-10 Remy van Dobben de Bruyn

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 give a geometric construction of tilting perverse sheaves using stratified Morse theory, torus actions, and nearby cycles.

Representation Theory · Mathematics 2007-05-23 David Nadler

In this paper we prove that the category of parity complexes on the flag variety of a complex connected reductive group is a "graded version" of the category of tilting perverse sheaves on the flag variety of the dual group, for any field…

Representation Theory · Mathematics 2015-02-09 Pramod N. Achar , Simon Riche

Let X be a smooth toric variety stratified by the torus action. This paper is a presentation of a description of the category Perv_X of perverse sheaves on X relatively to the fixed stratification. We define a category of representations of…

Algebraic Geometry · Mathematics 2010-03-17 Delphine Dupont

Let T be a torus over an algebraically closed field k of characteristic 0, and consider a projective T-module P(V). We determine when a projective toric subvariety X of P(V) is self-dual, in terms of the configuration of weights of V.

Algebraic Geometry · Mathematics 2014-02-26 Mathias Bourel , Alicia Dickenstein , Alvaro Rittatore

We study perverse sheaves of categories their connections to classical algebraic geometry. We show how perverse sheaves of categories encode naturally derived categories of coherent sheaves on $\mathbb{P}^1$ bundles, semiorthogonal…

Algebraic Geometry · Mathematics 2019-07-01 Andrew Harder , Ludmil Katzarkov

We show that there is a perverse sheaf on a fine moduli space of stable sheaves on a smooth projective Calabi-Yau 3-fold, which is locally the perverse sheaf of vanishing cycles for a local Chern-Simons functional, possibly after taking an…

Algebraic Geometry · Mathematics 2016-03-22 Young-Hoon Kiem , Jun Li

In this paper we propose a construction of a monoidal category of "free-monodromic" tilting perverse sheaves on (Kac-Moody) flag varieties in the setting of the "mixed modular derived category" introduced by the first and third authors.…

Representation Theory · Mathematics 2022-11-15 Pramod N. Achar , Shotaro Makisumi , Simon Riche , Geordie Williamson

We determine versal non-commutative deformations of some simple collections in the categories of perverse coherent sheaves arising from tilting generators for projective morphisms.

Algebraic Geometry · Mathematics 2018-06-14 Yujiro Kawamata

Achar has recently introduced a family of t-structures on the derived category of equivariant coherent sheaves on a $G$-scheme, generalizing the perverse coherent t-structures of Bezrukavnikov and Deligne. They are called \emph{staggered}…

Algebraic Geometry · Mathematics 2008-06-05 David Treumann

For any field $k$, we give an algebraic description of the category $\mathrm{Perv}_\mathscr{S}(S^n (\mathbb{C}^2),k)$ of perverse sheaves on the $n$-fold symmetric product of the plane $S^n(\mathbb{C}^2)$ constructible with respect to its…

Algebraic Geometry · Mathematics 2024-09-20 Tom Braden , Carl Mautner

The Shafarevich conjecture for a class of varieties over a number field posits the finitude of those with good reduction outside a finite set of primes. In the case of hypersurfaces in the torus $\mathbb{G}_m^n$, a natural class to consider…

Number Theory · Mathematics 2024-08-19 Caleb Ji

We further develop the general theory of the "mixed modular derived category" introduced by the authors in a previous paper in this series. We then use it to study positivity and Q-Koszulity phenomena on flag varieties.

Representation Theory · Mathematics 2014-08-20 Pramod N. Achar , Simon Riche

We prove a theorem relating torus-equivariant coherent sheaves on toric varieties to polyhedrally-constructible sheaves on a vector space. At the level of K-theory, the theorem recovers Morelli's description of the K-theory of a smooth…

Algebraic Geometry · Mathematics 2011-09-23 Bohan Fang , Chiu-Chu Melissa Liu , David Treumann , Eric Zaslow

Perverse schobers are categorifications of perverse sheaves. We construct a perverse schober on a partial compactification of the stringy K\"ahler moduli space (SKMS) associated by Halpern-Leistner and Sam to a quasi-symmetric…

Algebraic Geometry · Mathematics 2019-09-06 Špela Špenko , Michel Van den Bergh
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