Averaging with a time-dependent perturbation parameter

Motivated by recent problems in mathematical cosmology, in which temporal averaging methods are applied in order to analyze the future asymptotics of models which exhibit oscillatory behavior, we provide a theorem concerning the large-time behavior for solutions of a general class of systems. We thus propose our result to be applicable to a wide range of problems in spatially homogenous cosmology with oscillatory behavior. Mathematically the theorem builds upon the standard theory of averaging in non-linear dynamical systems.