On purely radiative space-times (Q1069479)

The existence of space-times representing pure gravitational radiation which comes in from infinity and interacts with itself is discussed. They are characterized as solutions of Einstein's vacuum field equations possessing a smooth structure at past null infinity which forms the ''future null cone at past timelike infinity with complete generators.'' The ''pure radiation problem'' is analysed where ''free initial data'' for Einstein's field equations are prescribed on the null cone at past time- like infinity. It is demonstrated how the pure radiation problem can be formulated as a local initial value problem for the symmetric hyperbolic system of reduced conformal vacuum field equations. Its solutions are uniquely determined by the free data.