ON FELLER PROCESSES WITH SAMPLE PATHS IN BESOV-SPACES

Under mild regularity assumptions on its domain the infinitesimal gene rator of a Feller process is known to be a pseudo-differential operato r. We give a simple condition on the symbol of the generator in order to characterize the smoothness of the sample paths of real-valued Fell er processes in terms of Besov spaces B-pq(s)(R). Our result extends p revious papers on the paths of Gaussian, symmetric a-stable [6], [20], and Levy processes [11].