Abstract. We study the realisation A of the operator A = ∆ − DΦ, D· in L 2 (Ω, µ) with Dirichlet boundary condition, where Ω is a possibly unbounded open set in R N , Φ is a semi-convex function and the measure dµ(x) = exp(−Φ(x)) dx lets A be formally self-adjoint. The main result is that A :