Gauge symmetry origin of Bäcklund transformations for Painlevé equations

Abstract

We identify the self-similarity limit of the second flow of sl(N)mKdVhierarchy with the periodic dressing chain thus establishing a connection to A(1) N-1 invariant Painlev'e equations. The A(1) N-1 Bcklund symmetries of dressing equations and Painlev'e equations are obtained in the self-similarity limit of gauge transformations of the mKdV hierarchy realized as zero-curvature equations on the loop algebra sl (N) endowed with a principal gradation.