Scalar products of symmetric functions and matrix integrals

We present relations between Hirota-type bilinear operators, scalar products on spaces of symmetric functions and integrals defining matrix model partition functions. Using the fermionic Fock space representation, a proof of the expansion of an associated class of KP and 2-Toda tau functions $\tau_{r,n}$ in a series of Schur functions generalizing the hypergeometric series is given and related to the scalar product formulae. It is shown how special cases of such $\tau$-functions may be identified as formal series expansions of partition functions. A closed form exapnsion of $\log \tau_{r,n}$ in terms of Schur functions is derived.Comment: LaTex file. 15 pgs. Based on talks by J. Harnad and A. Yu. Orlov at the workshop: Nonlinear evolution equations and dynamical systems 2002, Cadiz (Spain) June 9-16, 2002. To appear in proceedings. (Minor typographical corrections added, abstract expanded

Matrix integrals as Borel sums of Schur function expansions

The partition function for unitary two matrix models is known to be a double KP tau-function, as well as providing solutions to the two dimensional Toda hierarchy. It is shown how it may also be viewed as a Borel sum regularization of divergent sums over products of Schur functions in the two sequences of associated KP flow variables.Comment: PlainTex file. 8 pgs. Based on talk by J. Harnad at the workshop: Symmetry and Perturbation Theory 2002, Cala Gonoone (Sardinia), May 1-26, 2002. To appear in proceedings. (World Scientific, Singapore, eds. S. Abenda, G. Gaeta). Typographical correction made to formula (2.7) to include previously omitted powers of r and