PERIODIC SOLUTIONS FOR SOME PARTIAL NEUTRAL FUNCTIONAL DIFFERENTIAL EQUATIONS

In this work, we study the existence of periodic solutions for par- tial neutral functional dierential equation. We assume that the linear part is not necessarily densely defined and satisfies the Hille-Yosida condition. In the nonhomogeneous linear case, we prove that the existence of a bounded solution on R + implies the existence of a periodic solution. In nonlinear case, we use the concept of boundedness and ultimate boundedness to prove the existence of periodic solutions.