Entire solutions of the abstract Cauchy problem.
The existence of mean periodic functions in the sense of L. Schwartz, generated, in various ways, by an equicontinuous group or an equicontinuous cosine function forces the spectral structure of the infinitesimal generator of or . In particular, it is proved under fairly general hypotheses that the spectrum has no accumulation point and that the continuous spectrum is empty.
We establish the existence of mild, strong, classical solutions for a class of second order abstract functional differential equations with nonlocal conditions.
We give sufficient conditions for the existence of the fundamental solution of a second order evolution equation. The proof is based on stable approximations of an operator A(t) by a sequence of bounded operators.