Colliding plane gravitational and fluid waves

This thesis describes the collision and subsequent interaction of two waves which exhibit plane symmetry, according to the theory of general relativity. The properties of plane waves are discussed and the necessary field equations and boundary conditions describing this situation are formulated. Techniques are introduced by which exact solutions describing the collision of gravitational waves with constant and aligned polarization may be generated. By way of demonstrating these techniques, an explicit new solution is obtained. A complete integral of a family of solutions which are isomorphic to Gowdy cosmologies is derived, and another general class of solutions which are the analogue of the Weyl solutions for axisymmetric space-times is obtained. Exact solutions are also described for the collision of gravitational waves with arbitrary polarization when coupled with scalar fields or a type of null fluid that forms a stiff perfect fluid on interaction. A method for obtaining large families of solutions of this type from existing vacuum solutions using either of two potential functions is introduced, and examples of its application are given. The restriction of these stiff fluid solutions to the case where the waves have constant and aligned polarization allows the method to be generalised.