Robustness of nonuniform dichotomies with different growth rates

Abstract

For nonautonomous linear differential equations

v0 = A(t)v in a Banach space, we consider general exponential dichotomies that extend the notion of (uniform) exponential dichotomy in various ways. Namely, the new notion allows: stable and unstable behavior with respect to growth rates ec(t) for an arbitrary function (t); nonuniform exponential behavior, causing that any stability or conditional stability may be nonuniform; and different growth rates in the uniform and nonuniform parts of the dichotomy. Our objective is threefold:

1. to show that there is a large class of linear differential equations admitting this general exponential behavior;

2. to provide conditions for the existence of general dichotomies in terms of appropriate Lyapunov exponents;

3. to establish the robustness of the exponential behavior, that is, its persistence under sufficiently small linear perturbations.