Existence of a periodic solution for some partial functional differential equations with infinite delay

This paper deals with the existence of periodic solutions for some partial functional differential equations with infinite delay. We suppose that the linear part is nondensely defined and satisfies the Hille-Yosida condition. In the nonlinear case we give several criteria to ensure the existence of a periodic solution. In the nonhomogeneous linear case, we prove the existence of a periodic solution under the existence of a bounded solution. (C) 2001 Academic Press.