A SIMPLE SCHEME FOR GENERATING NONISOSPECTRAL FLOWS FROM THE ZERO CURVATURE REPRESENTATION

A simple method is described to construct from the zero curvature repr esentation nonisospectral (lambda(t) = lambda(n), n greater-than-or-eq ual-to 0, lambda is the spectral parameter) flows associated with a gi ven isospectral (lambda(t) = 0) hierarchy of integrable systems. Moreo ver further properties are exhibited. This method consists of searchin g for an initial vector field determined by a key equation provided th at the characteristic operator equation has solutions. We demonstrate the effectiveness of our method by applications to three hierarchies o f integrable systems as particular examples.