34 research outputs found
Large n limit of Gaussian random matrices with external source, Part III: Double scaling limit
We consider the double scaling limit in the random matrix ensemble with an
external source \frac{1}{Z_n} e^{-n \Tr({1/2}M^2 -AM)} dM defined on Hermitian matrices, where is a diagonal matrix with two eigenvalues of equal multiplicities. The value is critical since the eigenvalues
of accumulate as on two intervals for and on one
interval for . These two cases were treated in Parts I and II, where
we showed that the local eigenvalue correlations have the universal limiting
behavior known from unitary random matrix ensembles. For the critical case
new limiting behavior occurs which is described in terms of Pearcey
integrals, as shown by Br\'ezin and Hikami, and Tracy and Widom. We establish
this result by applying the Deift/Zhou steepest descent method to a -matrix valued Riemann-Hilbert problem which involves the construction of a
local parametrix out of Pearcey integrals. We resolve the main technical issue
of matching the local Pearcey parametrix with a global outside parametrix by
modifying an underlying Riemann surface.Comment: 36 pages, 9 figure
Non-intersecting squared Bessel paths and multiple orthogonal polynomials for modified Bessel weights
We study a model of non-intersecting squared Bessel processes in the
confluent case: all paths start at time at the same positive value , remain positive, and are conditioned to end at time at . In
the limit , after appropriate rescaling, the paths fill out a
region in the -plane that we describe explicitly. In particular, the paths
initially stay away from the hard edge at , but at a certain critical
time the smallest paths hit the hard edge and from then on are stuck to
it. For we obtain the usual scaling limits from random matrix
theory, namely the sine, Airy, and Bessel kernels. A key fact is that the
positions of the paths at any time constitute a multiple orthogonal
polynomial ensemble, corresponding to a system of two modified Bessel-type
weights. As a consequence, there is a matrix valued
Riemann-Hilbert problem characterizing this model, that we analyze in the large
limit using the Deift-Zhou steepest descent method. There are some novel
ingredients in the Riemann-Hilbert analysis that are of independent interest.Comment: 59 pages, 11 figure
On universality of local edge regime for the deformed Gaussian Unitary Ensemble
We consider the deformed Gaussian ensemble in which
is a hermitian matrix (possibly random) and is the Gaussian
unitary random matrix (GUE) independent of . Assuming that the
Normalized Counting Measure of converges weakly (in probability if
random) to a non-random measure with a bounded support and assuming
some conditions on the convergence rate, we prove universality of the local
eigenvalue statistics near the edge of the limiting spectrum of .Comment: 25 pages, 2 figure
An expansion for polynomials orthogonal over an analytic Jordan curve
We consider polynomials that are orthogonal over an analytic Jordan curve L
with respect to a positive analytic weight, and show that each such polynomial
of sufficiently large degree can be expanded in a series of certain integral
transforms that converges uniformly in the whole complex plane. This expansion
yields, in particular and simultaneously, Szego's classical strong asymptotic
formula and a new integral representation for the polynomials inside L. We
further exploit such a representation to derive finer asymptotic results for
weights having finitely many singularities (all of algebraic type) on a thin
neighborhood of the orthogonality curve. Our results are a generalization of
those previously obtained in [7] for the case of L being the unit circle.Comment: 15 pages, 1 figur
Relative asymptotics for orthogonal matrix polynomials with respect to a perturbed matrix measure on the unit circle
19 pages, no figures.-- MSC2000 codes: 42C05, 47A56.MR#: MR1970413 (2004b:42058)Zbl#: Zbl 1047.42021Given a positive definite matrix measure Ω supported on the unit circle T, then main purpose of this paper is to study the asymptotic behavior of L_n(\tilde{\Omega}) L_n(\Omega) -1} and \Phi_n(z, \tilde{\Omega}) \Phi_n(z, \tilde{\Omega}) -1} where , , M is a positive definite matrix and δ is the Dirac matrix measure. Here, Ln(·) means the leading coefficient of the orthonormal matrix polynomials Φn(z; •).Finally, we deduce the asymptotic behavior of in the case when M=I.The work of the second author was supported by Dirección General de Enseñanza Superior (DGES) of Spain under grant PB96-0120-C03-01 and INTAS
Project INTAS93-0219 Ext.Publicad
Differential equations for the radial limits in Z+2of the solutions of a discrete integrable system
Abstract:
A limiting property of the coefficients of the nearest-neighbor recurrence coefficients for the multiple orthogonal polynomials is studying. Namely, assuming existence of the limits along rays of the lattice nearest-neighbor coefficients, we describe the limit in terms of the solution of a system of ordinary differential equations. For Angelesco systems, the result is illustrated numerically.Note:
Research direction:Mathematical problems and theory of numerical method
Matrix Riemann-Hilbert Problems for Pade Approximants of Orthogonal Expansions
Abstract:
Markov-type functions generated by measures given on some interval are considered. We are constructing Pade approximants of orthogonal expansions for their Fourier series expansion by orthogonal polynomials on some other interval. Besides, we are studying both types of such constructions: linear Frobenius-Pade
approximants and nonlinear Fourier-Pade ones. We have obtained two main new results in this paper: complete set of orthogonality relations for Fourier-Pade approximants denominators, and also equivalent reformulation of the problems concerning Pade-Fourier approximants of orthogonal expansions in terms of matrix Riemann-Hilbert problems.Note:
Research direction:Mathematical problems and theory of numerical method