Sard′s Theorem for Hyper-Gevrey Functionals on the Wiener Space

Let (X, H, μ) be the Wiener space; we define "twisted Sobolev spaces" associated to certain compact operators on H. Wiener functionals belonging to one of these spaces are termed "hypersmooth"; we prove a measure-theoretic analog of Sard′s theorem for them. Our result applies in particular to solutions of Itô′s SDE′s with Gevrey class coefficients.