Brownian Manifolds, Negative Type and Geo-temporal Covariances
  We survey Brownian manifolds -- manifolds that can parametrise Brownian motion -- and those that cannot. We consider covariances of space-time processes, particularly those when space is the sphere -- geo-temporal processes. There are connections with functions of negative type. 
N. H. Bingham, Aleksander Mijatovi\'c, Tasmin L. Symons
math.PR