The Robin and Wentzell-Robin Laplacians on Lipschitz domains

Let.. RN be a bounded domain with Lipschitz boundary. We prove in the first part that a realization of the Laplacian with Robin boundary conditions partial derivative u/partial derivative nu + beta u = 0 on the boundary partial derivative Omega generates a holomorphic C-0-semigroup of angle pi/2 on C((Omega) over bar) if 0 < beta(0) <= beta is an element of L-infinity(partial derivative Omega). With the same assumption on Omega and assuming that 0 <= beta is an element of L-infinity(partial derivative Omega), we show in the second part that one can define a realization of the Laplacian on C(<(Omega)over bar>) with Wentzell-Robin boundary conditions Delta u + partial derivative u/partial derivative nu + beta u = 0 on the boundary.. and this operator generates a C-0-semigroup.