Out-of-time-order correlators in bipartite nonintegrable systems

Out-of-time-order correlators being explored as a measure of quantum chaos, are studied here in a coupled bipartite system. Each of the subsystems can be chaotic or regular and lead to very different out-of-time-order correlators growths both before and after the scrambling or the Ehrenfest time. We present preliminary results then on weakly coupled subsystems which have very different Lyapunov exponents. We also review the case when both the subsystems are strongly chaotic when a random matrix model can be pressed into service to derive an exponential relaxation to saturation.