The starting point for this article is a well-known example by M.~Renardy showing the failure of the equality $\omega(T)=s(A)$ for a first order perturbation to the wave equation, where $\omega(T)$ denotes the growth bound ...

Consider the Dirichlet problem for elliptic and parabolic equations in nondivergence form with variable coefficients in convex bounded domains of R^n. We prove solvability of the elliptic problem and maximal L^q-L^p-estimates ...

Let Ω be an exterior domain in It is shown that Ornstein-Uhlenbeck operators L generate C0-semigroups on Lp(Ω) for p ∈ (1, ∞) provided ∂Ω is smooth. The method presented also allows to determine the domain D(L) of L and ...