Almost periodicity of mild solutions of inhomogeneous periodic cauchy problems

We consider a mild solution u of a well-posed, inhomogeneous, Cauchy proble m, (u) over dot (t) = A(t) u(t) + f(t), on a Banach space X, where A(.) is periodic. For a problem on R+, we show that u is asymptotically almost peri odic if f is asymptotically almost periodic, ii is bounded, uniformly conti nuous and totally ergodic, and the spectrum of the monodromy operator V con tains only countably many points of the unit circle. For a problem on R, we show that a bounded, uniformly continuous solution u is almost periodic if f is almost periodic and various supplementary conditions are satisfied. W e also show that there is a unique bounded solution subject to certain spec tral assumptions on V, f and u. (C) 1999 Academic Press.