Browsing by Author "Varchenko, A."

Now showing 1 - 3 of 3
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    Cohomology classes of conormal bundles of Schubert varieties and Yangian weight functions
    (Springer, 2014-08) Rimányi, R.; Tarasov, Vitaly; Varchenko, A.; Mathematical Sciences, School of Science
    We consider the conormal bundle of a Schubert variety SI in the cotangent bundle T∗Gr of the Grassmannian Gr of k-planes in Cn. This conormal bundle has a fundamental class κI in the equivariant cohomology H∗T(T∗Gr). Here T=(C∗)n×C∗. The torus (C∗)n acts on T∗Gr in the standard way and the last factor C∗ acts by multiplication on fibers of the bundle. We express this fundamental class as a sum YI of the Yangian Y(gl2) weight functions (WJ)J. We describe a relation of YI with the double Schur polynomial [SI]. A modified version of the κI classes, named κ′I, satisfy an orthogonality relation with respect to an inner product induced by integration on the non-compact manifold T∗Gr. This orthogonality is analogous to the well known orthogonality satisfied by the classes of Schubert varieties with respect to integration on Gr. The classes (κ′I)I form a basis in the suitably localized equivariant cohomology H∗T(T∗Gr). This basis depends on the choice of the coordinate flag in Cn. We show that the bases corresponding to different coordinate flags are related by the Yangian R-matrix.
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    Elliptic and K-theoretic stable envelopes and Newton polytopes
    (Springer, 2019-03) Rimányi, R.; Tarasov, V.; Varchenko, A.; Mathematical Sciences, School of Science
    In this paper we consider the cotangent bundles of partial flag varieties. We construct the K -theoretic stable envelopes for them and also define a version of the elliptic stable envelopes. We expect that our elliptic stable envelopes coincide with the elliptic stable envelopes defined by M. Aganagic and A. Okounkov. We give formulas for the K -theoretic stable envelopes and our elliptic stable envelopes. We show that the K -theoretic stable envelopes are suitable limits of our elliptic stable envelopes. That phenomenon was predicted by M. Aganagic and A. Okounkov. Our stable envelopes are constructed in terms of the elliptic and trigonometric weight functions which originally appeared in the theory of integral representations of solutions of qKZ equations twenty years ago. (More precisely, the elliptic weight functions had appeared earlier only for the gl2 case.) We prove new properties of the trigonometric weight functions. Namely, we consider certain evaluations of the trigonometric weight functions, which are multivariable Laurent polynomials, and show that the Newton polytopes of the evaluations are embedded in the Newton polytopes of the corresponding diagonal evaluations. That property implies the fact that the trigonometric weight functions project to the K -theoretic stable envelopes.
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    On the Gaudin model associated to Lie algebras of classical types
    (AIP, 2016-10) Lu, Kang; Mukhin, Eugene; Varchenko, A.; Department of Mathematical Sciences, School of Science
    We derive explicit formulas for solutions of the Bethe ansatz equations of the Gaudin model associated to the tensor product of one arbitrary finite-dimensional irreducible module and one vector representation for all simple Lie algebras of classical type. We use this result to show that the Bethe ansatz is complete in any tensor product where all but one factor are vector representations and the evaluation parameters are generic.