Asymptotic Behaviour of Convolution Semigroups

In this paper, necessary and sufficient conditions are given for U * μ^*n to converge uniformly on the real axis; here $\mu$ is a nonsingular probability measure on ℝ, and U is a Banach space valued L^∞-function. A connection to uniform convergence of Cesaro mean values is shown. By applying the results to extended orbits of bounded C_0-semigroups on a Banach space X one can relate both kernel and range of the respective generator with those of the derivative operator on L^∞(X). Ergodic theorems and consequences for subordinated semigroups, in particular for holomorphic semigroups, are deduced.