The stochastic limit of quantum spin systems

The stochastic limit for the system of spins interacting with a boson field is investigated. In the finite volume an application of the stochastic golden rule shows that in the limit the dynamics of a quantum system is described by a quantum white noise equation that after taking of normal order is equivalent to quantum stochastic differential equation (QSDE). For the quantum Langevin equation the dynamics is well defined and is a quantum flow on the infinite lattice system.