“…In Section 5 we will restrict to the case where F is a gradient perturbation, namely it has a potential. In this case the invariant measure ν is a weighted Gaussian measure and it is possible to associate a quadratic form Q 2 to N 2 , see for example [2,3,9,10,20,25,26,27,30,31,40]. Under some additional hypotheses (Hypotheses 5.5) we will define the Sobolev space W 1,2 C (X, ν), and we will show that there exists a quadratic form Q 2 on W 1,2 C (X, ν) such that…”