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A. Varchenko

Publications and source records attributed to A. Varchenko.

At least 73 records · Page 4Linked to original sources
arXiv2005

Poincare-Birkhoff-Witt expansions of the canonical elliptic differential form

We study the canonical U(\n)-valued elliptic differential form, whose projections to different Kac-Moody algebras are key ingredients of the hypergeometric integral solutions of elliptic KZ differential equations and Bethe ansatz constructions. We explicitly determine the coefficients of the projections in the simple Lie algebras A_r, B_r, C_r, D_r in a conveniently chosen Poincare-Birkhoff-Witt basis. As an application we give a new formula for eigenfunctions of Hamiltonians of the Calogero-Moser model.

math.RT↗
arXiv2004

Identities between q-hypergeometric and hypergeometric integrals of different dimensions

Given complex numbers $m_1,l_1$ and nonnegative integers $m_2,l_2$, such that $m_1+m_2=l_1+l_2$, for any $a,b=0, ... ,\min(m_2,l_2)$ we define an $l_2$-dimensional Barnes type q-hypergeometric integral $I_{a,b}(z,μ;m_1,m_2,l_1,l_2)$ and an $l_2$-dimensional hypergeometric integral $J_{a,b}(z,μ;m_1,m_2,l_1,l_2)$. The integrals depend on complex parameters $z$ and $μ$. We show that $I_{a,b}(z,μ;m_1,m_2,l_1,l_2)$ equals $J_{a,b}(e^μ,z;l_1,l_2,m_1,m_2)$ up to an explicit factor, thus establishing an equality of $l_2$-dimensional q-hypergeometric and $m_2$-dimensional hypergeometric integrals. The identity is based on the $(gl_k,gl_n)$ duality for the qKZ and dynamical difference equations.

math.QA↗
arXiv2004

Dynamical differential equations compatible with rational qKZ equations

For the Lie algebra $gl_N$ we introduce a system of differential operators called the dynamical operators. We prove that the dynamical differential operators commute with the $gl_N$ rational quantized Knizhnik-Zamolodchikov difference operators. We describe the transformations of the dynamical operators under the natural action of the $gl_N$ Weyl group.

math.QA↗
arXiv2004

Identities for hypergeometric integrals of different dimensions

Given complex numbers $m_1,l_1$ and positive integers $m_2,l_2$, such that $m_1+m_2=l_1+l_2$, we define $l_2$-dimensional hypergeometric integrals $I_{a,b}(z;m_1,m_2,l_1,l_2)$, $a,b=0,...,\min(m_2,l_2)$, depending on a complex parameter $z$. We show that $I_{a,b}(z;m_1,m_2,l_1,l_2)=I_{a,b}(z;l_1,l_2,m_1,m_2)$, thus establishing an equality of $l_2$ and $m_2$-dimensional integrals. This identity allows us to study asymptotics of the integrals with respect to their dimension in some examples. The identity is based on the $(gl_k,gl_n)$ duality for the KZ and dynamical differential equations.

math.QA↗
arXiv2003

Critical points of functions, sl_2 representations, and Fuchsian differential equations with only univalued solutions

Let a second order Fuchsian differential equation with only univalued solutions have finite singular points at z_1, ..., z_n with exponents (a_1,b_1), ..., (a_n,b_n). Let the exponents at infinity be (A,B). Then for fixed generic z_1,...,z_n, the number of such Fuchsian equations is equal to the multiplicity of the irreducible sl_2 representation of dimension |A-B| in the tensor product of irreducible sl_2 representations of dimensions |a_1-b_1|, >..., |a_n-b_n|. To show this we count the number of critical points of a suitable function which plays the crucial role in constructions of the hypergeometric solutions of the sl_2 KZ equation and of the Bethe vectors in the sl_2 Gaudin model. As a byproduct of this study we conclude that the Bethe vectors form a basis in the space of states for the sl_2 inhomogeneous Gaudin model.

math.QA↗
arXiv2002

Multiplication Formulas for the Elliptic Gamma Function

The elliptic gamma function is a generalization of the Euler gamma function. Its trigonometric and rational degenerations are the Jackson q-gamma function and the Euler gamma function. We prove multiplication formulas for the elliptic gamma function, whose degenerations are the Gauss-Askey multiplication formula for the Euler and trigonometric gamma functions.

math.QA↗
arXiv2002

Solutions to the XXX type Bethe ansatz equations and flag varieties

We consider a version of the A_N Bethe equation of XXX type and introduce a reproduction procedure constructing new solutions of this equation from a given one. The set of all solutions obtained from a given one is called a population. We show that a population is isomorphic to the sl_{N+1} flag variety and that the populations are in one-to-one correspondence with intersection points of suitable Schubert cycles in a Grassmanian variety. We also obtain similar results for the root systems B_N and C_N. Populations of B_N and C_N type are isomorphic to the flag varieties of C_N and B_N types respectively.

math.QA↗
arXiv2002

Critical points of master functions and flag varieties

We consider critical points of master functions associated with integral dominant weights of Kac-Moody algebras and introduce a generating procedure constructing new critical points starting from a given one. The set of all critical points constructed from a given one is called a population. We formulate a conjecture that a population is isomorphic to the flag variety of the Langlands dual Kac-Moody algebra and prove the conjecture for algebras $sl_{N+1}, so_{2N+1}$, and $sp_{2N}$. We show that populations associated with a collection of integral dominant $sl_{N+1}$-weights are in one to one correspondence with intersection points of suitable Schubert cycles in a Grassmannian variety.

math.QA↗
arXiv2002

How to regularize singular vectors and kill the dynamical Weyl group

We study the meromorphic family of intertwining operators between Verma modules and their products with finite-dimensional ones. A regularizing operator, acting in a finite dimensional module U, makes this family holomorphic, and conjugates the dynamical Weyl group operators to constant operators. We prove uniqueness property for regularizing operators, and construct them explicitly for the Lie algebra sl_3.

math.QA↗
arXiv2001

Small Elliptic Quantum Group $e_{tau,γ}(sl_N)$

The small elliptic quantum group $e_{τ,γ}(sl_N)$, introduced in the paper, is an elliptic dynamical analogue of the universal enveloping algebra $U(sl_n)$. We define highest weight modules, Verma modules and contragradient modules over $e_{τ,γ}(sl_N)$, the dynamical Shapovalov form for $e_{τ,γ}(sl_N)$ and the contravariant form for highest weight $e_{τ,γ}(sl_N)$-modules. We show that any finite-dimensional $sl_N$-module and any Verma module over $sl_N$ can be lifted to the corresponding $e_{τ,γ}(sl_N)$-module on the same vector space. For the elliptic quantum group $E_{τ,γ}(sl_N)$ we construct the evaluation morphism $E_{τ,γ}(sl_N)\to e_{τ,γ}(sl_N)$, thus making any $e_{τ,γ}(sl_N)$-module into an evaluation $E_{τ,γ}(sl_N)$-module.

math.QA↗
arXiv2001

Solutions of Trigonometric KZ Equations satisfy Dynamical Difference Equations

The trigonometric KZ equations associated to a Lie algebra \g depend on a parameter λin \h where \h is a Cartan subalgebra of \g. A system of dynamical difference equations with respect to λcompatible with the KZ equations is introduced in Tarasov and Varchenko. We prove that the standard hypergeometric solutions of the trigonometric KZ equations associated to sl_N also satisfy the dynamical difference equations.

math.QA↗
arXiv2000

Difference Equations Compatible with Trigonometric KZ Differential Equations

The trigonometric KZ equations associated with a Lie algebra $\g$ depend on a parameter $λ\in\h$ where $\h\subset\g$ is the Cartan subalgebra. We suggest a system of dynamical difference equations with respect to $λ$ compatible with the KZ equations. The dynamical equations are constructed in terms of intertwining operators of $\g$-modules.

math.QA↗
arXiv2000

Differential Equations Compatible with KZ Equations

We define a system of "dynamical" differential equations compatible with the KZ differential equations. The KZ differential equations are associated to a complex simple Lie algebra $\mathbf{g}$. These are equations on a function of $n$ complex variables $z_i$ taking values in the tensor product of $n$ finite dimensional $\mathbf{g}$-modules. The KZ equations depend on the "dual" variable in the Cartan subalgebra of $\mathbf{g}$. The dynamical differential equations are differential equations with respect to the dual variable. We prove that the standard hypergeometric solutions of the KZ equations also satisfy the dynamical equations. As an application we give a new determinant formula for the coordinates of a basis of hypergeometric solutions.

math.QA↗