ON STABILITY OF THE EQUAIONS Bu0(t) = Au(t)

Abstract

The stability of solutions of the equation $Bu^0(t) = Au(t)$ is considered, where A and B are closed linear operators on a Banach space. Under the well-posedness condition it is proved that if the imaginary part of the spectrum of the pencil (¸B ¡ A) is countable, then a bounded uniformly continuous solution u(t) of the equation is asymptotically almost periodic if and only if the functions e¸ tu(t), (¸ 2 iR), have uniformly convergent means. A condition of exponential stability also is given when the generalized eigenvectors and associated root vectors of the linear pencil (¸B ¡ A) form a Riesz basis.