In this paper we study weakly hyperbolic second order equations with time dependent
irregular coefficients. This means assuming that the coefficients are less regular than Hölder …

In this paper we study the well-posedness of the Cauchy problem for a wave equation with
multiplicities and space-dependent irregular coefficients. As in Garetto and Ruzhansky …

In this paper we investigate the well-posedness of the Cauchy problem for the wave
equation for sums of squares of vector fields on compact Lie groups. We obtain the loss of …

In this paper we continue the analysis of non-diagonalisable hyperbolic systems initiated in
[,]. Here we assume that the system has discontinuous coefficients or more in general …

In this paper we analyse the well-posedness of the Cauchy problem for a rather general
class of hyperbolic systems with space-time dependent coefficients and with multiple …

This paper is devoted to the study of the inhomogeneous wave equation with singular (less
than continuous) time dependent coefficients. Particular attention is given to the role of the …

This paper deals with a problem of finding a bounded in a strip solution to a system of
second order hyperbolic evolution equations, where the matrix coefficient of the spatial …

In this paper, we study first-order hyperbolic systems of any order with multiple
characteristics (weakly hyperbolic) and time-dependent analytic coefficients. The main …

We study hyperbolic systems with multiplicities and smooth coefficients. In the case of non-
analytic, smooth coefficients, we prove well-posedness in any Gevrey class and when the …

Symmetrizers for hyperbolic operators are obtained by diagonalizing the Bézoutian matrix of
the principal symbols and its derivatives. Such diagonal symmetrizers are applied to the …