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Correlation Functions of Harish-Chandra Integrals over the Orthogonal and the Symplectic Groups

A. Prats Ferrer, B. Eynard, P. Di Francesco, J. -B. Zuber

math-pharXiv:math-ph/0610049

Abstract

The Harish-Chandra correlation functions, i.e. integrals over compact groups of invariant monomials prod trXp1 Omega Yq1 Omegadagger Xp2 ... with the weight exp trX Omega Y Omegadagger are computed for the orthogonal and symplectic groups. We proceed in two steps. First, the integral over the compact group is recast into a Gaussian integral over strictly upper triangular complex matrices (with some additional symmetries), supplemented by a summation over the Weyl group. This result follows from the study of loop equations in an associated two-matrix integral and may be viewed as the adequate version of Duistermaat-Heckman's theorem for our correlation function integrals. Secondly, the Gaussian integration over triangular matrices is carried out and leads to compact determinantal expressions.

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