The classical Bondi-Penrose approach to the gravitational radiation theory in asymptotically flat spacetimes is recalled and recent advances in the proofs of the existence of such spacetimes are briefly reviewed. We then mention the unique role of the boost-rotation symmetric spacetimes, representing uniformly accelerated objects, as the only explicit radiative solutions known which are asymptotically flat; they are used as test beds in numerical relativity and approximation methods. The main part of the review is devoted to the examples of radiative fields in the vacuum spacetimes with positive cosmological constant. Type N solutions are analyzed by using the equation of geodesic deviation. Both these and RobinsonTrautman solutions of type II are shown to approach de Sitter universe asymptotically. Recent work on the the radiative fields due to uniformly accelerated charges in de Sitter spacetime ("cosmological Born's solutions") is reviewed and the properties of these fields are discussed with a perspective to characterize general features of radiative fields near a de Sitter-like infinity.
IntroductionAfter several important contributions to the gravitational radiation theory in the late 1950's and early 1960's by Pirani, Bondi, Robinson, Trautman and others, a landmark paper by Bondi et al 4 appeared in which radiative properties of isolated (spatially bounded) axisymmetric systems were studied along outgoing null hypersurfaces u = constant, with u representing a retarded time function. An ansatz was made that the asymptotically Minkowski metric along u = constant can be expanded in inverse powers * An extended version of the invited talk given by J. B. at the 10th Greek Relativity Meeting in Kallithea, Chalkidiki, May 2002. Secs. 1, 2, 4 and 6 are in part based on the reviews quoted as Refs. 1, 2 and 3.