Integral equation of quantum stochastic process

To describe stochastic quantum processes I propose an integral equation of Volterra type which is not generally transformable to any differential one. The process is a composition of ordinary quantum evolution which admits presence of a quantum bath and reductions to pure states. It is proved that generically solutions stabilize asymptotically for $t\to +\infty$ to a universal limit - the projection onto the state with maximal available entropy. A number of typical methods of finding solutions of the equation are proposed.