On non-autonomous strongly damped wave equations with a uniform attractor and some averaging

In this paper we study the existence of a uniform attractor for strongly damped wave equations with a time-dependent driving force. If the time-dependent function is translation compact, then in a certain parameter region, the uniform attractor of the system has a simple structure: it is the closure of all the values of the unique, bounded complete trajectory of the wave equation. And it attracts any bounded set exponentially. At the same time, we consider the strongly damped wave equations with rapidly oscillating external force gε(x, t) = g(x, t, t/ε) having the average g0(x, t) as ε →0+. We prove that the Hausdorff distance between the uniform attractor Aε of the original equation and the uniform attractor A0 of the averaged equation is less than O(ε1/2). We mention, in particular, that the obtained results can be used to study the usual damped wave equations. © 2007 Elsevier Inc. All rights reserved