36 research outputs found
Integrable Fredholm Operators and Dual Isomonodromic Deformations
The Fredholm determinants of a special class of integral operators K
supported on the union of m curve segments in the complex plane are shown to be
the tau-functions of an isomonodromic family of meromorphic covariant
derivative operators D_l. These have regular singular points at the 2m
endpoints of the curve segments and a singular point of Poincare index 1 at
infinity. The rank r of the vector bundle over the Riemann sphere on which they
act equals the number of distinct terms in the exponential sums entering in the
numerator of the integral kernels. The deformation equations may be viewed as
nonautonomous Hamiltonian systems on an auxiliary symplectic vector space M,
whose Poisson quotient, under a parametric family of Hamiltonian group actions,
is identified with a Poisson submanifold of the loop algebra Lgl_R(r) with
respect to the rational R-matrix structure. The matrix Riemann-Hilbert problem
method is used to identify the auxiliary space M with the data defining the
integral kernel of the resolvent operator at the endpoints of the curve
segments. A second associated isomonodromic family of covariant derivative
operators D_z is derived, having rank n=2m, and r finite regular singular
points at the values of the exponents defining the kernel of K. This family is
similarly embedded into the algebra Lgl_R(n) through a dual parametric family
of Poisson quotients of M. The operators D_z are shown to be analogously
associated to the integral operator obtained from K through a Fourier-Laplace
transform.Comment: PlainTeX 32g
Isomonodromy aspects of the tt* equations of Cecotti and Vafa I. Stokes data
We describe all smooth solutions of the two-function tt*-Toda equations (a
version of the tt* equations, or equations for harmonic maps into
SL(n,R)/SO(n)) in terms of (i) asymptotic data, (ii) holomorphic data, and
(iii) monodromy data. This allows us to find all solutions with integral Stokes
data. These include solutions associated to nonlinear sigma models (quantum
cohomology) or Landau-Ginzburg models (unfoldings of singularities), as
conjectured by Cecotti and Vafa.Comment: 35 pages, 3 figures. Minor revisions for compatibility with the
recently posted Part II (arXiv:1312.4825
Integro-Difference Equation for a correlation function of the spin- Heisenberg XXZ chain
We consider the Ferromagnetic-String-Formation-Probability correlation
function (FSFP) for the spin- Heisenberg XXZ chain. We construct a
completely integrable system of integro-difference equations (IDE), which has
the FSFP as a -function. We derive the associated Riemann-Hilbert problem
and obtain the large distance asymptotics of the FSFP correlator in some
limiting cases.Comment: 14 pages, latex+epsf, 1 figur
Determinant representation for a quantum correlation function of the lattice sine-Gordon model
We consider a completely integrable lattice regularization of the sine-Gordon
model with discrete space and continuous time. We derive a determinant
representation for a correlation function which in the continuum limit turns
into the correlation function of local fields. The determinant is then embedded
into a system of integrable integro-differential equations. The leading
asymptotic behaviour of the correlation function is described in terms of the
solution of a Riemann Hilbert Problem (RHP) related to the system of
integro-differential equations. The leading term in the asymptotical
decomposition of the solution of the RHP is obtained.Comment: 30 pages Latex2e, 2 Figures, epsf. Significantly extended and revised
versio
Random Words, Toeplitz Determinants and Integrable Systems. I
It is proved that the limiting distribution of the length of the longest
weakly increasing subsequence in an inhomogeneous random word is related to the
distribution function for the eigenvalues of a certain direct sum of Gaussian
unitary ensembles subject to an overall constraint that the eigenvalues lie in
a hyperplane.Comment: 15 pages, no figure
The tt*-Toda equations of A_n type
In previous articles we have studied the A_n tt*-Toda equations
(topological-antitopological fusion equations of Toda type) of Cecotti and
Vafa, giving details mainly for n=3. Here we give a proof of the existence and
uniqueness of global solutions for any n, and a new treatment of their
asymptotic data, monodromy data, and Stokes data.Comment: 68 pages, 7 figures. Typographical errors have been corrected in this
versio
Connection formulae for the radial Toda equations I
This paper is the first in a forthcoming series of works where the authors
study the global asymptotic behavior of the radial solutions of the 2D periodic
Toda equation of type . The principal issue is the connection formulae
between the asymptotic parameters describing the behavior of the general
solution at zero and infinity. To reach this goal we are using a fusion of the
PDE analysis and the Riemann-Hilbert nonlinear steepest descent method of Deift
and Zhou which is applicable to 2D Toda in view of its Lax integrability. A
principal technical challenge is the extension of the nonlinear steepest
descent analysis to Riemann-Hilbert problems of matrix rank greater than .
In this paper, we meet this challenge for the case (the rank case)
and it already captures the principal features of the general case.Comment: 68 pages, 16 figure