Time dependent loss of derivatives for hyperbolic operators with non-regular coefficients

Abstract

In this paper we will study the Cauchy problem for strictly hyperbolic operators with low regularity coe fficients in any space dimension N ≥ 1. We will suppose the coe fficients to be log-Zygmund continuous in time and log-Lipschitz continuous in space. Paradifferential calculus with parameters will be the main tool to get energy estimates in Sobolev spaces and these estimates will present a time-dependent loss of derivatives.