MATRIX MODELS AS INTEGRABLE SYSTEMS - FROM UNIVERSALITY TO GEOMETRODYNAMICAL PRINCIPLE OF STRING THEORY

Matrix models are equivalent to certain integrable theories, partition functions being equal to certain tau-functions, i.e., the section of determinant bundles over infinite-dimensional Grassmannian. These tau-functions are evaluated at the points of Grassmannian, where high symmetry arises. In the case of one-matrix models the symmetry is isomorphic to Borel subgroup of a Virasoro group. The orbits of the group are in one-to-one correspondence with the types of "multicritical" behavior in the continuum limit. Interrelation between tau-functions in different models and their continuum limit is discussed in some details. We also discuss the implications for dynamical interpolation between various string models (CFT's), to be described in terms of geometrical quantization of Fairlie-like W infinity-algebras.