Hydrodynamic limit of the symmetric exclusion process on complete Riemannian manifolds and principal bundles

Abstract: We define the symmetric exclusion process (SEP) on random neighbourhood graphs drawn from Poisson point processes on complete connected Riemannian manifolds equipped with a Gibbs reference measure. We obtain diffusions with drift induced by the potential of the Gibbs measure as hydrodynamic limits. This is a consequence of the duality between the (SEP) and random walks approximating weighted Laplacians. We also lift the (SEP) to principal bundles, and we obtain horizontal diffusions with drift as hydrodynamic limits. Examples include the orthonormal frame bundle with the horizontal Laplacian which plays a central role in the Eells-Elworthy-\'Emery construction of Riemannian Brownian motion.