arXiv subjects

M. Finkelberg

Publications and source records attributed to M. Finkelberg.

6 recordsLinked to original sources

arXiv2012

Uhlenbeck spaces via affine Lie algebras

Let $G$ be an almost simple simply connected group over $\BC$, and let $\Bun^a_G(\BP^2,\BP^1)$ be the moduli scheme of principal $G$-bundles on the projective plave $\BP^2$, of second Chern class $a$, trivialized along a line $\BP^1\subset \BP^2$. We define the Uhlenbeck compactification $\fU^a_G$ of $\Bun^a_G(\BP^2,\BP^1)$, which classifies, roughly, pairs $(\F_G,D)$, where $D$ is a 0-cycle on $\BA^2=\BP^2-\BP^1$ of degree $b$, and $\F_G$ is a point of $\Bun^{a-b}_G(\BP^2,\BP^1)$, for varying $b$. In addition, we calculate the stalks of the Intersection Cohomology sheaf of $\fU^a_G$. To do that we give a geometric realization of Kashiwara's crystals for affine Kac-Moody algebras.

math.AG↗

arXiv2000

Intersection cohomology of Drinfeld's compactifications

Let $X$ be a smooth complete curve, $G$ be a reductive group and $P\subset G$ a parabolic. Following Drinfeld, one defines a compactification $\widetilde{\on{Bun}}_P$ of the moduli stack of $P$-bundles on $X$. The present paper is concerned with the explicit description of the Intersection Cohomology sheaf of $\widetilde{\on{Bun}}_P$. The description is given in terms of the combinatorics of the Langlands dual Lie algebra $\check{\mathfrak g}$.

math.AG↗

arXiv1995

Localization of $\frak{u}$-modules. IV. Localization on $\Bbb{P}^1$

This article is a sequel to hep-th/9411050, q-alg/9412017, q-alg/9503013. Given a collection of $m$ finite factorizable sheaves $\{\CX_k\}$, we construct here some perverse sheaves over configuration spaces of points on a projective line $\BP^1$ with $m$ additional marked points. We announce here (with sketch proof) the computation of the cohomology spaces of these sheaves. They turn out to coincide with certain "semiinfinite" $\Tor$ spaces of the corresponding $\fu$-modules. As a corollary, we get a description of local systems of conformal blocks in WZW models in genus $0$ (cf. ~\cite{ms}) as natural subquotients of some semisimple local systems of geometric origin. In particular, these local systems are semisimple themselves.

q-alg↗

arXiv1995

Localization of $\frak{u}$-modules. III. Tensor categories arising from configuration spaces

This article is a sequel to hep-th/9411050, q-alg/9412017. In Chapter 1 we associate with every Cartan matrix of finite type and a non-zero complex number $ζ$ an abelian artinian category $\FS$. We call its objects {\em finite factorizable sheaves}. They are certain infinite collections of perverse sheaves on configuration spaces, subject to a compatibility ("factorization") and finiteness conditions. In Chapter 2 the tensor structure on $\FS$ is defined using functors of nearby cycles. It makes $\FS$ a braided tensor category. In Chapter 3 we define, using vanishing cycles functors, an exact tensor functor $$Φ:\FS\lra\CC$$ to the category $\CC$ connected with the corresponding quantum group. In Chapter 4 we show that $Φ$ is an equivalence. Some proofs are only sketched.

q-alg↗

arXiv1995

Localization of $\frak{u}$-modules. II. Configuration spaces and quantum groups

This paper is a sequel to "Localization of $\frak{u}$-modules. I", hep-th/9411050. We are starting here the geometric study of the tensor category $\cal{C}$ associated with a quantum group (corresponding to a Cartan matrix of finite type) at a root of unity. The main results establish isomorphisms between homogeneous components of irreducible objects in $\cal{C}$ and spaces of vanishing cycles at the origin of certain Goresky-MacPherson sheaves on configuration spaces; establish isomorphisms of the stalks at the origin of the above GM sheaves with certain Hochschild complexes (which compute the Hochschild homology of a certain "triangular" subalgebra of our quantum group with coefficients in the coresponding irreducible representation); establish the analogous results for tensor products of irreducibles. In geometry, the tensor product of representations corresponds to a "fusion" of sheaves on configuration spaces --- operation defined using the functor of nearby cycles.

q-alg↗

arXiv1994

Localization of $\frak{u}$-modules. I. Intersection cohomology of real arrangements

This paper is the first in a series. The main goal of the series is to present a geometric construction of certain remarkable tensor categories arising from quantum groups coresponding to the value of deformation parameter $q$ equal to a root of unity. In the present paper we study perverse sheaves over a complex affine space which are smooth along the stratification determined by a finite arrangement of complex affine hyperplanes defined by real equations. In particular, we construct explicitely (in terms of combinatorial data) complexes computing cohomology of Goresky-MacPherson extensions of one-dimensional local systems over the complement of hyperplanes.

hep-th↗