The main result of this paper is the following: any `weighted' Riemannian manifold $(M,g,\mu)$ - i.e. endowed with a generic non-negative Radon measure $\mu$ - is `infinitesimally Hilbertian', which means that its associated Sobolev space $W^{ 1,2}(M,g,\mu)$ is a Hilbert space. We actually prove a stronger result: the abstract tangent module (\`a la Gigli) associated to any weighted reversible Finsler manifold $(M,F,\mu)$ can be isometrically embedded into the space of all measurable sections of the tangent bundle of $M$ that are $2$-integrable with respect to $\mu$.
Categories: math.DG