Exact non-singular waves in the anti-de Sitter universe

A class of radiative solutions of Einstein's field equations with a negativ e cosmological constant and a pure radiation is investigated. The space-tim es, which generalize the Defrise solution, represent exact gravitational wa ves which interact with null matter and propagate in the anti-de Sitter uni verse. Interestingly, these solutions have homogeneous and non-singular wav e-fronts for all freely moving observers. We also study properties of sandw ich and impulsive waves which can be constructed in this class of space-tim es.