Analyticity of absorption semigroups (Q1891650)

If \(U\) is an analytic positive \(C_0\) semigroup on \(L^p(\Omega)\) generated by \(T\) and \(V\) is a measurable function on \(\Omega\), then by Voigt's perturbation theory we can construct \(U_V(t)\), the positive \(C_0\) semigroup generated (formally) by \(T-V\). The author gives conditions under which \(U_V\) has an analytic extension, with application (among others) to the absorption semigroup generated by the heat operator.