Incoherent Dispersive Shocks in the Spectral Evolution of Random Waves

We predict theoretically and numerically the existence of incoherent dispersive shock waves. They manifest themselves as an unstable singular behavior of the spectrum of incoherent waves that evolve in a noninstantaneous nonlinear environment. This phenomenon of ‘‘spectral wave breaking’’ develops in the weakly nonlinear regime of the random wave. We elaborate a general theoretical formulation of these incoherent objects on the basis of a weakly nonlinear statistical approach: a family of singular integrodifferential kinetic equations is derived, which provides a detailed deterministic description of the incoherent dispersive shock wave phenomenon.