374 research outputs found
Multivariable Christoffel-Darboux Kernels and Characteristic Polynomials of Random Hermitian Matrices
We study multivariable Christoffel-Darboux kernels, which may be viewed as
reproducing kernels for antisymmetric orthogonal polynomials, and also as
correlation functions for products of characteristic polynomials of random
Hermitian matrices. Using their interpretation as reproducing kernels, we
obtain simple proofs of Pfaffian and determinant formulas, as well as Schur
polynomial expansions, for such kernels. In subsequent work, these results are
applied in combinatorics (enumeration of marked shifted tableaux) and number
theory (representation of integers as sums of squares).Comment: This is a contribution to the Vadim Kuznetsov Memorial Issue on
Integrable Systems and Related Topics, published in SIGMA (Symmetry,
Integrability and Geometry: Methods and Applications) at
http://www.emis.de/journals/SIGMA
The combinatorics of associated Hermite polynomials
We develop a combinatorial model of the associated Hermite polynomials and
their moments, and prove their orthogonality with a sign-reversing involution.
We find combinatorial interpretations of the moments as complete matchings,
connected complete matchings, oscillating tableaux, and rooted maps and show
weight-preserving bijections between these objects. Several identities,
linearization formulas, the moment generating function, and a second
combinatorial model are also derived.Comment: [v1]: 18 pages, 16 figures; presented at FPSAC 2007 [v2]: Some minor
errors fixed (thanks Bill Chen, Jang Soo Kim) and text rearranged and cleaned
up; no real content changes [v3]: fixed typos, to appear in European J.
Combinatoric
A new multivariable 6-psi-6 summation formula
By multidimensional matrix inversion, combined with an A_r extension of
Jackson's 8-phi-7 summation formula by Milne, a new multivariable 8-phi-7
summation is derived. By a polynomial argument this 8-phi-7 summation is
transformed to another multivariable 8-phi-7 summation which, by taking a
suitable limit, is reduced to a new multivariable extension of the
nonterminating 6-phi-5 summation. The latter is then extended, by analytic
continuation, to a new multivariable extension of Bailey's very-well-poised
6-psi-6 summation formula.Comment: 16 page
Dressing method and the coupled KP hierarchy
The coupled KP hierarchy, introduced by Hirota and Ohta, are investigated by
using the dressing method. It is shown that the coupled KP hierarchy can be
reformulated as a reduced case of the 2-component KP hierarchy.Comment: 11 pages, LaTeX, no figure
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