Seminars Sorted by Series

This talk will form part of a series of three talks focusing on Broué’s Abelian Defect Group Conjecture, which concerns the modular representation theory of finite groups. We will pay particular attention here to the ‘geometric’ form of the...

In this second talk about Broué’s Abelian Defect Group Conjecture, we will explain its geometric version in the case of finite groups of Lie type: the equivalence should be induced by the cohomology complex of Deligne-Lusztig varieties. This was...

We will discuss $p$-local representation theory and conjectures of Broue and Alperin, the latter been inspired by finite groups of Lie type in characteristic $p$. The issue is the extent to which the category of representations can be reconstructed...

We will discuss the conjecture of Broue relating modular representations of finite groups of Lie type in non-defining characteristic to those of normalizers of Levi subgroups, with a focus on $GL_n$. The categories of representations can be related...

This is the first talk in a series of three talks towards understanding Bezrukavnikov-Finkelberg's derived geometric Satake equivalence. In this talk, we recall the geometry of equal characteristic affine Grassmannians and some of the ingredients of...

This is the second talk in a series of three talks on the derived Satake. I will give an overview of an article by Ginzburg which laid the foundational ideas for this equivalence.

This is the third talk in a series of three talks on the derived Satake equivalence. I will give an overview of the article of Bezrukavnikov and Finkelberg which explains how the equivariant derived category of the affine Grassmannian can be...

This is the last talk towards understanding Bezrukavnikov-Finkelberg's derived geometric Satake equivalence. With the preparations from previous talks, we will introduce two filtrations: a topological filtration on the equivariant cohomology and an...

This talk will be an exposition of a recent paper of Bezrukavnikov-Gaitsgory-Mirkovic-Riche-Rider giving an Iwahori-Whittaker model for the Satake category. The main point is that their argument works for modular coefficients. I will give some...

Before the "geometric Satake equivalence" there was a decategorified version of it which however contained most of its essential features. In my talk I will talk about some of the ideas which have led to this theory. In particular I will explain the...

Motivated by a formal similarity between the Hard Lefschetz theorem and the geometric Satake equivalence we study vector spaces that are graded by a weight lattice and are endowed with linear operators in simple root directions. We allow field...

The talk is about convolution in the setting of geometric representation theory. What are its formal properties? As a starting point, let $G$ be a group and let $D(G)$ be the derived category of constructible sheaves on it. Convolution turns $D(G)$...

Smith theory is a type of equivariant localization with respect to a cyclic group of prime order $p$, with coefficients in a field of the same characteristic $p$. It has been the source of various recent advances in modular representation theory and...

The linkage principle says that the category of representations of a reductive group $G$ in positive characteristic decomposes into "blocks" controlled by the affine Weyl group. We will discuss the beautiful geometric proof of this result that Simon...

Wall-crossing functors on the principal block of category $O$ give an action of the (finite) Hecke category. If one knows enough about the Hecke category, one can deduce the Kazhdan-Lusztig conjectures from the existence of this action. This is a...

In the upcoming series of talks we discuss some equivalences by Bezrukavnikov between categories of coherent sheaves on Steinberg varieties and of perverse sheaves on the affine flag variety. In this talk I discuss the decategorified isomorphism...

This is the second in a series of talks on "two realizations." We discuss equivariantization and de-equivariantization for a group $G$, which relate categories with $G$-actions and categories with RepG-actions, and how this relates to the notion of...

A theorem of Bernstein identifies the center of the affine Hecke algebra of a reductive group $G$ with the Grothendieck ring of the tensor category of representations of the dual group $G^\vee$. Gaitsgory constructed a functor which categrorifies...

We will discuss the following theorems concerning colimits taken in the infinity-category of monoidal DG-categories. (No familiarity with infinity-categories will be required or assumed.) The affine Hecke category is the monoidal colimit of its...

The anti-spherical modules over the affine Hecke algebras admit two different realizations: one realization is in terms of the space of Whittaker functions on the affine flag manifolds and the other realization, due to Kazhdan-Lusztig, is in terms...

In this talk we will begin the discussion of the results in Bezrukavnikov's "On Two Geometric Realizations of the Affine Hecke algebra". We will put all the previous tools described in this series of talks together to construct the equivalence of...

I will start with a few comments on the proof of the equivalence presented in the previous talks. Then I will focus on the description of the abelian category of perverse sheaves on the affine flag variety on the coherent side, where the answer is...

The goal of this talk is two-fold. We state a parabolic version of the two realizations theorem and sketch a proof. This version relates Iwahori-constructible sheaves on parabolic affine flag variety to coherent sheaves on a parabolic version of the...

Perverse sheaves and intersection cohomology are central objects in geometric representation theory. This talk is about their long-lost K-theoretic cousins, called K-motives. We will discuss definitions and basic properties of K-motives and explore...

For homogeneous affine Springer fibers (those with $G_m$ symmetry), we realize them as Lagrangian cycles inside ambient symplectic varieties, and make sense of microlocal sheaves supported on these affine Springer fibers. We also propose a...

I will report on a project joint with Roman Bezrukavnikov (and partly with Laura Rider) aiming at constructing a variant for positive-characteristic coefficients of the equivalence constructed by Bezrukavnikov in "On two geometric realizations of an...

I will report on a joint work in progress with K. Coulembier and V. Ostrik. We show that a symmetric tensor category in characteristic $p > 0$ admits a fiber functor to the Verlinde category (semisimplification of $Rep(Z/p)$) if and only if it has...