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A. Yu. Orlov

Publications and source records attributed to A. Yu. Orlov.

47 records · Page 3Linked to original sources
arXiv2002

Tau Functions and Matrix Integrals

We consider solvable matrix models. We generalize Harish-Chandra-Itzykson-Zuber and certain other integrals (Gross-Witten integral and integrals over complex matrices) using the notion of tau function of matrix argument. In this case one can reduce the matrix integral to the integral over eigenvalues, which in turn is certain tau function. The resulting tau function may be analyzed either by the method of orthogonal polynomials or by the Schur functions expansion method.

math-ph↗
arXiv2002

Matrix integrals as Borel sums of Schur function expansions

The partition function for unitary two matrix models is known to be a double KP tau-function, as well as providing solutions to the two dimensional Toda hierarchy. It is shown how it may also be viewed as a Borel sum regularization of divergent sums over products of Schur functions in the two sequences of associated KP flow variables.

nlin.SI↗
arXiv2002

Matrix Integrals, Symmetric Functions theory and matrix integrals

We consider certain scalar product of symmetric functions which is parameterized by a function $r$ and an integer $n$. One the one hand we have a fermionic representation of this scalar product. On the other hand we get a representation of this product with the help of multi-integrals. This gives links between a theory of symmetric functions, soliton theory and models of random matrices (such as a model of normal matrices).

nlin.SI↗
arXiv2000

Fermionic representation for basic hypergeometric functions related to Schur polynomials

We present the fermionic representation for the q-deformed hypergeometric functions related to Schur polynomials considered by S.Milne \cite{Milne}. For $q=1$ these functions are also known as hypergeometric functions of matrix argument which are related to zonal spherical polynomials for $GL(N,C)/U(N)$ symmetric space. We show that these multivariable hypergeometric functions are tau-functions of the KP hierarchy. At the same time they are the ratios of Toda lattice tau-functions considered by Takasaki in \cite{Tinit}, \cite{T} evaluated at certain values of higher Toda lattice times. The variables of the hypergeometric functions are related to the higher times of those hierarchies via Miwa change of variables. The discrete Toda lattice variable shifts parameters of hypergeometric functions. Hypergeometric functions of type ${}_pF_s$ can be also viewed as group 2-cocycle for the $Ψ$DO on the circle of the order $p-s \leq 1$ (the group times are higher times of TL hierarchy and the arguments of hypergeometric function). We get the determinant representation and the integral representation of special type of KP tau-functions, these results generalize some of Milne's results in \cite{Milne}. We write down a system of linear differential and difference equations for these tau-functions (string equations). We present also fermionic representation for special type of Gelfand-Graev hypergeometric functions.

nlin.SI↗
arXiv2000

Multivariate hypergeometric functions as tau functions of Toda lattice and Kadomtsev-Petviashvili equation

We present the q-deformed multivariate hypergeometric functions related to Schur polynomials as tau-functions of the KP and of the two-dimensional Toda lattice hierarchies. The variables of the hypergeometric functions are the higher times of those hierarchies. The discrete Toda lattice variable shifts parameters of hypergeometric functions. The role of additional symmetries in generating hypergeometric tau-functions is explained.

math-ph↗
arXiv1997

Flag Spaces in KP Theory and Virasoro Action on \det D_j and Segal-Wilson τ-Function

It is well-known that the algebra of vector fields on the circle acts on the space of Riemann surfaces with a marked point and a local parameter at this point. We show that this action has a natural realization in the soliton theory, indeed it coincides with the action of some non-isospectral Kadomtsev-Petviashvili symmetries on the finite-gap solutions. A technique based on the so-called Cauchy-Baker-Akhiezer kernel is developed. The deformations of the τ-function corresponding to the Baker-Akhiezer forms of tensor weight j generate representations of the Virasoro algebra with a central charge 6j^2-6j+1. A system including the Kadomtsev-Petviashvili hierarchy and the Toda lattice simultaneously is considered. The Virasoro representations corresponding to such a system explicitly depend on an extra discrete time t_0. The tau-function for this system is defined in terms of infinite dimensional flag spaces, generalizing the grassmanians.

math-ph↗
arXiv1997

$P_\infty$ algebra of KP, free fermions and 2-cocycle in the Lie algebra of pseudodifferential operators

The symmetry algebra $P_\infty = W_\infty \oplus H \oplus I_\infty$ of integrable systems is defined. As an example the classical Sophus Lie point symmetries of all higher KP equations are obtained. It is shown that one (``positive'') half of the point symmetries belongs to the $W_\infty$ symmetries while the other (``negative'') part belongs to the $I_\infty$ ones. The corresponing action on the tau-function is obtained for the positive part of the symmetries. The negative part can not be obtained from the free fermion algebra. A new embedding of the Virasoro algebra into $gl(\infty )$n describes conformal transformations of the KP time variables. A free fermion algebra cocycle is described as a PDO Lie algebra cocycle.

solv-int↗
arXiv1995

Dispersionful analogues of Benney's equations and $N$-wave systems

We recall Krichever's construction of additional flows to Benney's hierarchy, attached to poles at finite distance of the Lax operator. Then we construct a ``dispersionful'' analogue of this hierarchy, in which the role of poles at finite distance is played by Miura fields. We connect this hierarchy with $N$-wave systems, and prove several facts about the latter (Lax representation, Chern-Simons-type Lagrangian, connection with Liouville equation, $τ$-functions).

solv-int↗
arXiv1994

Symmetries of the Kadomstev-Petviashvili Hierarchy

The relation between the $\widehat{\Sl}(\infty)$ algebra of flows commuting with the KP hierarchy and the Kac-Moody-Virasoro Lie point symmetries of individual equations is established. This is used to calculate the point symmetries for all equations in the hierarchy.

hep-th↗