On a vanishing conjecture appearing in the geometric Langlands correspondence

Let $X$ be a smooth complete curve, and let $Bun_n$ be the moduli stack of rank $n$ vector bundles on $X$. Let $E$ be a local system on $X$. In a recent paper of E.Frenkel, K.Vilonen and the author, it was shown that the vanishing of a certian functor $Av_E^d$ acting from the category $D(Bun_n)$ to itself, implies the geometric Langlands conjecture. In this paper we establish the required vanishing result. Our proof works for sheaves with char=0 coefficients, or with torsion coefficients when the parameter $d$ is less than the characteristic.Comment: Revised versio

Operads, Grothendieck topologies and Deformation theory

The idea of the work is to find an invariant way to pass from deformation theory to cohomology, which does not use any explicit cocycles. The appropriate cohomology theory is based on considering sheaves on a certain site. An advantage of the approach is that it enables one to give a simultanious treatement to all types of algebras. As an application, we prove the PBW theorem in cases where it is not yet known.Comment: 13 pages, AmsTe

A "strange" functional equation for Eisenstein series and miraculous duality on the moduli stack of bundles

We show that the failure of the usual Verdier duality on Bun(G) leads to a new duality functor on the category of D-modules, and we study its relation to the operation of Eisenstein series

Spherical varieties and Langlands duality

Let G be a connected reductive complex algebraic group. This paper is devoted to the space Z of meromorphic quasimaps from a curve into an affine spherical G-variety X. The space Z may be thought of as an algebraic model for the loop space of X. In this paper, we associate to X a connected reductive complex algebraic subgroup $\check H$ of the dual group $\check G$. The construction of $\check H$ is via Tannakian formalism: we identify a certain tensor category Q(Z) of perverse sheaves on Z with the category of finite-dimensional representations of $\check H$. Combinatorial shadows of the group $\check H$ govern many aspects of the geometry of X such as its compactifications and invariant differential operators. When X is a symmetric variety, the group $\check H$ coincides with that associated to the corresponding real form of G via the (real) geometric Satake correspondence

The category of singularities as a crystal and global Springer fibers

We prove the "Gluing Conjecture" on the spectral side of the categorical geometric Langlands correspondence. The key tool is the structure of crystal on the category of singularities, which allows to reduce the conjecture to the question of homological triviality of certain homotopy types. These homotopy types are obtained by gluing from a global version of Springer fibers

D-modules on the affine Grassmannian and representations of affine Kac-Moody algebras

Let ${\mathfrak g}$ be a simple Lie algebra. For a level $\kappa$ (thought of as a symmetric ${\mathfrak g}$-invariant form of ${\mathfrak g}$), let $\hat{\mathfrak g}_\kappa$ be the corresponding affine Kac-Moody algebra. Let $Gr_G$ be the affine Grassmannian of ${\mathfrak g}$, and let $D_\kappa(Gr_G)-mod$ be the category of $\kappa$-twisted right D-modules on $Gr_G$. By taking global sections of a D-module, we obtain a functor $\Gamma:D_\kappa(Gr_G)-mod\to {\mathfrak g}_\kappa-mod$. It is known that this functor is exact and faithful when $\kappa$ is negative or irrational. In this paper, we show that the functor $\Gamma$ is exact and faithful also when $\kappa$ is the critical level.Comment: Revised version; to appear in Duke Math. Journa

Differential operators and the loop group via chiral algebras

Let $G$ be an algebraic group and let $\widetilde{\mathfrak g}$ be the corresponding affine algebra on some level. Consider the induced module V:=Ind^{\widetilde{\mathfrak g}}_{{\mathfrak g}[[t]](O_{G[[t]]}), where $O_{G[[t]]}$ is the ring of regular functions on the group $G[[t]]$. In this paper we show that $V$ is naturally a vertex operator algebra, which is "responsible" for D-modules on the loop group $G((t))$. Using the techiques of VOA we show that $V$ is in fact a bimodule over the affine algebra. In addition, we show that $V$ possesses a remarkable property related to its BRST reduction with respect to $\widetilde{\mathfrak g}$. This paper has a considerable intersection with a recent preprint of Gorbunov, Malikov and Schechtman.Comment: Revised version, Section 6 adde

On Ginzburg's Lagrangian construction of representations of GL(n)

In 1991 V. Ginzburg observed that one can realize irreducible representations of the group $GL(n,C)$ in the cohomology of certain Springer's fibers for the group GL(d) (for all natural d). However, Ginzburg's construction of the action of GL(n) on this cohomology was a bit artificial (he defined the action of Chevalley generators of the Lie algebra gl(n) on the corresponding cohomology by certain explicit correspondences, following the work of A. Beilinson, G. Lusztig and R. MacPherson, who gave a similar construction of the quantum group $U_q(gl(n))$). In this note we give a very simple geometric definition of the action of the whole group GL(n,C) on the above cohomology and simplify the Ginzburg's results.Comment: 7 pages, LaTeX2

Representations of algebraic groups over a 2-dimensional local field

We introduce a categorical framework for the study of representations of $G_F$, where $G$ is a reductive group, and \bF is a 2-dimensional local field, i.e. $F=K((t))$, where $K$ is a local field. Our main result says that the space of functions on $G_F$, which is an object of a suitable category of representations of $G_F$ with the respect to the action of $G_F$ on itself by left translations, becomes a representation of a certain central extension of $G_F$, when we consider the action by right translations.Comment: Revised versio

Geometric realizations of Wakimoto modules at the critical level

We study the Wakimoto modules over the affine Kac-Moody algebras at the critical level from the point of view of the equivalences of categories proposed in our previous works, relating categories of representations and certain categories of sheaves. In particular, we describe explicitly geometric realizations of the Wakimoto modules as Hecke eigen-D-modules on the affine Grassmannian and as quasi-coherent sheaves on the flag variety of the Langlands dual group