Stochastic Quantization and Critical Dynamics

Some years ago Nelson [1] proposed an alternative formulation of quantum mechanics based on the theory of Markov random processes (stochastic mechanics). This is interesting for several reasons. Among others we mention the formulation of quantum physics through a language which requires no drastic departures from the concepts of classical physics, the access to the powerful mathematical tools of probability theory for the derivation of rigorous results, and last but not least the expectation that new physical insights may be opened by the new language. Without elaborating on these very interesting aspects of stochastic quantization here we take a rather pragmatic point of view. We regard stochastic mechanics as a formal construct, entirely equivalent to the Schrodinger formulation of quantum mechanics, which gives a representation of the quantum mechanical states in terms of Markov random processes. The point is that the stochastic representation of the states proves to be useful in the kind of problems considered in the following.