Self-consistent transport tensors for collective motion in several dimensions

We present a microscopic study of slow collective dynamics of large scale and at finite intrinsic excitations. We compute transport coefficients for average motion within linear response theory. Specifically we address problems encountered for multidimensional cases, like the question of how to separate low-frequency modes from the rest. We show how collective response tensors can be analyzed to obtain expressions for the tensors of inertia, friction and local stiffness. The latter are computed at finite frequency, thus avoiding the zero-frequency limit and, hence, a strict Markov limit. Finally, we interpret our results and discuss their physical significance.