An L2 theory for differential forms on path spaces I ✩

An L2 theory of differential forms is proposed for the Banach manifold of continuous paths on a Riemannian manifold M furnished with its Brownian motion measure. Differentiation must be restricted to certain Hilbert space directions, the H-tangent vectors. To obtain a closed exterior differential operator the relevant spaces of differential forms, the H-forms, are perturbed by the curvature of M. A Hodge decomposition is given for L2 H-one-forms, and the structure of H-two-forms is described. The dual operator d∗ is analysed in terms of a natural connection on the H-tangent spaces. Malliavin calculus is a basic tool. © 2007 Elsevier Inc. All rights reserved.