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E. Vasserot

Publications and source records attributed to E. Vasserot.

At least 19 recordsLinked to original sources
arXiv2017

On the number of points of nilpotent quiver varieties over finite fields

We give a closed expression for the number of points over finite fields (or the motive) of the Lusztig nilpotent variety associated to any quiver, in terms of Kac's A-polynomials. When the quiver has 1-loops or oriented cycles, there are several possible variants of the Lusztig nilpotent variety, and we provide formulas for the point count of each. This involves nilpotent versions of the Kac A-polynomial, which we introduce and for which we give a closed formula similar to Hua's formula for the usual Kac A-polynomial. Finally we compute the number of points over a finite field of the various stratas of the Lusztig nilpotent variety involved in the geometric realization of the crystal graph.

math.RT↗
arXiv2015

On the center of quiver-Hecke algebras

We compute the equivariant cohomology ring of the moduli space of framed instantons over the affine plane. It is a Rees algebra associated with the center of cyclotomic degenerate affine Hecke algebras of type A. We also give some related results on the center of quiver Hecke algebras and cohomology of quiver varieties.

math.RT↗
arXiv2010

Hall algebras of curves, commuting varieties and Langlands duality

We construct an isomorphism between the (universal) spherical Hall algebra of a smooth projective curve of genus g and a convolution algebra in the (equivariant) K-theory of the genus g commuting varieties C_{{gl}_r}={(x_i, y_i) \in {gl}_r^{2g}; \sum_{i=1}^g [x_i,y_i]=0}. We can view this isomorphism as a version of the geometric Langlands duality in the formal neighborhood of the trivial local system, for the group GL_r. We extend this to all reductive groups and we compute the image, under our correspondence, of the skyscraper sheaf supported on the trivial local system.

math.QA↗
arXiv2006

Riemann-Roch for real varieties

If E is a C^\infty complex vector bundle on an oriented C^\infty manifold Σ, diffeomorphic to a circle, then the space of sections of E has a canonical polarization in the sense of Pressley and Segal and so one has its determinantal gerbe with lien C^*, the group of nonzero complex numbers. If q:Σ-->B is a smooth family of circles as above and E is a vector bundle on Σ, then the smooth direct image q_*(E) is an infinite-dimensional bundle with fibers as above and so we have its determinantal gerbe on B with lien being the sheaf of invertible complex valued C^\infty functions, it gives a class in H^3(B, Z). In this paper we consider a family q:Σ-->B as above but with fibers being compact oriented C^\infty manifolds of dimension d. For a bundle E on Σone expects q_*(E) to possess a determinantal d-gerbe and hence to give a class in H^{d+2}(B, Z). We construct directly, by means of a version of the Chern-Weil theory, the real version of this would be class. We further prove a real version of the Grothendieck-Riemann-Roch theorem describing this class as a direct image of a certain characteristic class of E.

math.DG↗
arXiv2006

Formal loops IV: Chiral differential operators

We relate the gerbe of sheaves of chiral differential operators (CDO) on a algebraic variety X, studied by Gorbounov, Malikov and Schechtman, to the determinantal gerbe of the formal loop space LX introduced in our earlier paper. The liens of the two gerbes are related by a version of the symplectic action homomorphism. The determinantal gerbe of LX has a factorization structure in the spirit of Beilinson and Drinfeld. In our identification, sheaves of CDO correspond to factorizing objects of this factorization gerbe.

math.AG↗
arXiv2005

Formal loops III: Factorizing functions and the Radon transform

To any algebraic variety X and and closed 2-form ωon X, we associate the "symplectic action functional" T(ω) which is a function on the formal loop space LX introduced by the authors in math.AG/0107143. The correspondence ω--> T(ω) can be seen as a version of the Radon transform. We give a characterization of the functions of the form T(ω) in terms of factorizability (infinitesimal analog of additivity in holomorphic pairs of pants) as well as in terms of vertex operator algebras. These results will be used in the subsequent paper which will relate the gerbe of chiral differential operators on X (whose lien is the sheaf of closed 2-forms) and the determinantal gerbe of the tangent bundle of LX (whose lien is the sheaf of invertible functions on LX). On the level of liens this relation associates to a closed 2-form ωthe invertible function exp T(ω).

math.AG↗
arXiv2005

Formal loops II: A local Riemann-Roch theorem for determinantal gerbes

If V is a bundle of Tate vector spaces over a base B, its determinantal gerbe has a class C_1(V) in the second cohomology group of the sheaf of invertible functions which can be seen as the Deligne cohomology H^3(B, Z(2)). An example of such a "Tate bundle" can be obtained from a finite rank vector bundle E on the product of B and a punctured formal disk. Our main result identifies the corresponding C_1(V) with the cohomological direct image of ch_2(E), the second Chern character of E. It can be seen as a "local" version of the Riemann-Roch-Grothendieck theorem for a family of curves. This theorem explains the results of Gorbounov, Malikov and Schechtman relating ch_2 of the tangent bundle of an algebraic variety X to the existence of a sheaf of chiral differential operators. To be precise, it implies that the determinantal anomaly of the formal loop space of X is the transgression of ch_2(TX).

math.AG↗
arXiv2004

Vertex algebras and the formal loop space

We introduce an algebro-geometric version of the free loop space for any scheme X of finite type. This is an ind-scheme of ind-infinite type containing the scheme of formal germs of curves on X. Then, we give a direct geometric construction, for smooth X, of the chiral de Rham complex of X (introduced by Malikov, Schechtman and Vaintrob).

math.AG↗
arXiv2000

On the action of the dual group on the cohomology of perverse sheaves on the affine grassmannian

It was proved by Ginzburg and Mirkovic-Vilonen that the $G(O)$-equivariant perverse sheaves on the affine grassmannian of a connected reductive group $G$ form a tensor category equivalent to the tensor category of finite dimensional representations of the dual group $G^\vee$. The proof use the Tannakian formalism. The purpose of this paper is to construct explicitely the action of $G^\vee$ on the global cohomology of a perverse sheaf.

math.AG↗
arXiv1999

Kleinian singularities, derived categories and Hall algebras

We describe the derived category of coherent sheaves on the minimal resolution of the Kleinian singularity associated to a finite subgroup G of SL(2). Then, we give an application to the Euler-characteristic version of the Hall algebra of the category of coherent sheaves on an algebraic surface.

math.AG↗