411 research outputs found
Combinatorial Formulas for Macdonald and Hall-Littlewood Polynomials of Types A and C. Extended Abstract
A breakthrough in the theory of (type A) Macdonald polynomials is due to
Haglund, Haiman and Loehr, who exhibited a combinatorial formula for these
polynomials in terms of fillings of Young diagrams. Recently, Ram and Yip gave
a formula for the Macdonald polynomials of arbitrary type in terms of the
corresponding affine Weyl group. In this paper, we show that a
Haglund-Haiman-Loehr type formula follows naturally from the more general
Ram-Yip formula, via compression. Then we extend this approach to the
Hall-Littlewood polynomials of type C, which are specializations of the
corresponding Macdonald polynomials at q=0. We note that no analog of the
Haglund-Haiman-Loehr formula exists beyond type A, so our work is a first step
towards finding such a formula
Richard Stanley through a crystal lens and from a random angle
We review Stanley's seminal work on the number of reduced words of the
longest element of the symmetric group and his Stanley symmetric functions. We
shed new light on this by giving a crystal theoretic interpretation in terms of
decreasing factorizations of permutations. Whereas crystal operators on
tableaux are coplactic operators, the crystal operators on decreasing
factorization intertwine with the Edelman-Greene insertion. We also view this
from a random perspective and study a Markov chain on reduced words of the
longest element in a finite Coxeter group, in particular the symmetric group,
and mention a generalization to a poset setting.Comment: 11 pages; 3 figures; v2 updated references and added discussion on
Coxeter-Knuth grap
Tridiagonalized GUE matrices are a matrix model for labeled mobiles
It is well-known that the number of planar maps with prescribed vertex degree
distribution and suitable labeling can be represented as the leading
coefficient of the -expansion of a joint cumulant of traces of
powers of an -by- GUE matrix. Here we undertake the calculation of this
leading coefficient in a different way. Firstly, we tridiagonalize the GUE
matrix in the manner of Trotter and Dumitriu-Edelman and then alter it by
conjugation to make the subdiagonal identically equal to . Secondly, we
apply the cluster expansion technique (specifically, the
Brydges-Kennedy-Abdesselam-Rivasseau formula) from rigorous statistical
mechanics. Thirdly, by sorting through the terms of the expansion thus
generated we arrive at an alternate interpretation for the leading coefficient
related to factorizations of the long cycle . Finally, we
reconcile the group-theoretical objects emerging from our calculation with the
labeled mobiles of Bouttier-Di Francesco-Guitter.Comment: 42 pages, LaTeX, 17 figures. The present paper completely supercedes
arXiv1203.3185 in terms of methods but addresses a different proble
Schur-Weyl duality and the heat kernel measure on the unitary group
We establish a convergent power series expansion for the expectation of a
product of traces of powers of a random unitary matrix under the heat kernel
measure. These expectations turn out to be the generating series of certain
paths in the Cayley graph of the symmetric group. We then compute the
asymptotic distribution of a random unitary matrix under the heat kernel
measure on the unitary group U(N) as N tends to infinity, and prove a result of
asymptotic freeness result for independent large unitary matrices, thus
recovering results obtained previously by Xu and Biane. We give an
interpretation of our main expansion in terms of random ramified coverings of a
disk. Our approach is based on the Schur-Weyl duality and we extend some of our
results to the orthogonal and symplectic cases
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