Journal of the
Korean Mathematical Society JKMS

We establish the existence of $C^1$ stable invariant manifolds for differential equations $u'=A(t)u+f(t,u,\lambda)$ obtained from sufficiently small $C^1$ perturbations of a \emph{nonuniform} exponential dichotomy. Since any linear equation with nonzero Lyapunov exponents has a nonuniform exponential dichotomy, this is a very general assumption. We also establish the $C^1$ dependence of the stable manifolds on the parameter $\lambda$. We emphasize that our results are optimal, in the sense that the invariant manifolds are as regular as the vector field. We use the fiber contraction principle to establish the smoothness of the invariant manifolds. In addition, we can also consider linear perturbations, and thus our results can be readily applied to the robustness problem of nonuniform exponential dichotomies.

Keywords: growth rates, nonuniform exponential dichotomies, parameter dependence, stable manifolds

MSC numbers: Primary 37D10, 37D25, 34D99

Supported by: Supported by FCT/Portugal through UID/MAT/04459/2013.