The elliptic Gaudin system with spin

The elliptic Gaudin model was obtained as the Hitchin system on an elliptic curve with two fixed points. In the present paper the algebraic-geometrical structure of the system with two fixed points is clarified. We identify this system with poles dynamics of the finite gap solutions of Davey-Stewartson equation. The solutions of this system in terms of theta-functions and the action-angle variables are constructed. We also discuss the geometry of its degenerations.Comment: 17 pages in Late

Riemann bilinear form and Poisson structure in Hitchin-type systems

In this paper we reinterpret the Poisson structure of the Hitchin-type system in cohomological terms. The principal ingredient of a new interpretation in the case of the Beauville system is the meromorphic cohomology of the spectral curve, and the main result is the identification of the Riemann bilinear form and the symplectic structure of the model. Eventual perspectives of this approach lie in the quantization domain.Comment: 15 page

Universal R-matrix formalism for the spin Calogero-Moser system and its difference counterpart

The expression of the quantum Ruijsenaars-Schneider Hamiltonian is obtained in the framework of the dynamical $R$-matrix formalism. This generalizes to the case of $U_q(sl_n)$ the result obtained by O. Babelon, D. Bernard and E. Billey for $U_q(sl_2)$ which is the higher difference Lame operator. The general method involved is the universal $R$-matrix construction.Comment: 9 pages in Late

Quantum generic Toda system

The Toda chains take a particular place in the theory of integrable systems, in contrast with the linear group structure for the Gaudin model this system is related to the corresponding Borel group and mediately to the geometry of flag varieties. The main goal of this paper is to reconstruct a "spectral curve" in a wider context of the generic Toda system. This appears to be an efficient way to find its quantization which is obtained here by the technique of quantum characteristic polynomial for the Gaudin model and an appropriate AKS reduction. We discuss also some relations of this result with the recent consideration of the Drinfeld Zastava space, the monopole space and corresponding Borel Yangian symmetries.Comment: 9 page

On the Lie-formality of Poisson manifolds

Starting from the problem of describing cohomological invariants of Poisson manifolds we prove in a sense a ``no-go'' result: the differential graded Lie algebra of de Rham forms on a smooth Poisson manifold is formal.Comment: 21 page

Quantum spectral curves, quantum integrable systems and the geometric Langlands correspondence

The spectral curve is the key ingredient in the modern theory of classical integrable systems. We develop a construction of the ``quantum spectral curve'' and argue that it takes the analogous structural and unifying role on the quantum level also. In the simplest, but essential case the ``quantum spectral curve'' is given by the formula "det"(L(z)-dz) [Talalaev04] (hep-th/0404153). As an easy application of our constructions we obtain the following: quite a universal receipt to define quantum commuting hamiltonians from the classical ones, in particular an explicit description of a maximal commutative subalgebra in U(gl(n)[t])/t^N and in U(\g[t^{-1}])\otimes U(t\g[t]); its relation with the center on the of the affine algebra; an explicit formula for the center generators and a conjecture on W-algebra generators; a receipt to obtain the q-deformation of these results; the simple and explicit construction of the Langlands correspondence; the relation between the ``quantum spectral curve'' and the Knizhnik-Zamolodchikov equation; new generalizations of the KZ-equation; the conjecture on rationality of the solutions of the KZ-equation for special values of level. In the simplest cases we observe the coincidence of the ``quantum spectral curve'' and the so-called Baxter equation. Connection with the KZ-equation offers a new powerful way to construct the Baxter's Q-operator.Comment: 54 pp. minor change

Universal G-oper and Gaudin eigenproblem

This paper is devoted to the eigenvalue problem for the quantum Gaudin system. We prove the universal correspondence between eigenvalues of Gaudin Hamiltonians and the so-called G-opers without monodromy in general gl(n) case modulo a hypothesys on the analytic properties of the solution of a KZ-type equation. Firstly we explore the quantum analog of the characteristic polynomial which is a differential operator in a variable $u$ with the coefficients in U(gl(n))^{\otimes N}. We will call it "universal G-oper". It is constructed by the formula "Det"(L(u)-\partial_u) where L(u) is the quantum Lax operator for the Gaudin model and "Det" is appropriate definition of the determinant. The coefficients of this differential operator are quantum Gaudin Hamiltonians obtained by one of the authors (D.T. hep-th/0404153). We establish the correspondence between eigenvalues and $G$-opers as follows: taking eigen-values of the Gaudin's hamiltonians on the joint eigen-vector in the tensor product of finite-dimensional representation of gl(n) and substituting them into the universal G-oper we obtain the scalar differential operator (scalar G-oper) which conjecturally does not have monodromy. We strongly believe that our quantization of the Gaudin model coincides with quantization obtained from the center of universal enveloping algebra on the critical level and that our scalar G-oper coincides with the G-oper obtained by the geometric Langlands correspondence, hence it provides very simple and explicit map (Langlands correspondence) from Hitchin D-modules to G-opers in the case of rational base curves. It seems to be easy to generalize the constructions to the case of other semisimple Lie algebras and models like XYZ.Comment: 15 pages, the status of some statements change

Rational Lax operators and their quantization

We investigate the construction of the quantum commuting hamiltonians for the Gaudin integrable model. We prove that [Tr L^k(z), Tr L^m(u) ]=0, for k,m < 4 . However this naive receipt of quantization of classically commuting hamiltonians fails in general, for example we prove that [Tr L^4(z), Tr L^2(u) ] \ne 0. We investigate in details the case of the one spin Gaudin model with the magnetic field also known as the model obtained by the "argument shift method". Mathematically speaking this method gives maximal Poisson commutative subalgebras in the symmetric algebra S(gl(N)). We show that such subalgebras can be lifted to U(gl(N)), simply considering Tr L(z)^k, k\le N for N<5. For N=6 this method fails: [Tr L_{MF}(z)^6, L_{MF}(u)^3]\ne 0 . All the proofs are based on the explicit calculations using r-matrix technique. We also propose the general receipt to find the commutation formula for powers of Lax operator. For small power exponents we find the complete commutation relations between powers of Lax operators.Comment: 30 page

Functional relations on anisotropic Potts models: from Biggs formula to Zamolodchikov equation

We explore several types of functional relations on the family of multivariate Tutte polynomials: the Biggs formula and the star-triangle ($Y-\Delta$) transformation at the critical point $n=2.$ We deduce the theorem of Matiyasevich and its inverse from the Biggs formula, apply this relation to construct the recursion on the parameter $n$. We provide two different proofs of the Zamolodchikov tetrahedron equation satisfied by the star-triangle transformation in the case of $n=2$ multivariate Tutte polynomial, extend the latter to the case of valency 2 points and show that the Biggs formula and the star-triangle transformation commute.Comment: 30 pages, 17 figures, minor change

Bethe ansatz and Isomonodromic deformations

We study symmetries of the Bethe equations for the Gaudin model appeared naturally in the framework of the geometric Langlands correspondence under the name of Hecke operators and under the name of Schlesinger transformations in the theory of isomonodromic deformations, and particularly in the theory of Painlev\'e transcendents.Comment: 14 pages, extended version of the talk given at CQIS-2008, the hypothesis prove