We expose a functional integration method for the averaging of continuous
products P^t of N×N random matrices. As an application, we
compute exactly the statistics of the Lyapunov spectrum of P^t. This
problem is relevant to the study of the statistical properties of various
disordered physical systems, and specifically to the computation of the
multipoint correlators of a passive scalar advected by a random velocity field.
Apart from these applications, our method provides a general setting for
computing statistical properties of linear evolutionary systems subjected to a
white noise force field.Comment: Latex, 9 page