Curvature collineations in certain gravitational space-times

It has been shown that the space-times formed from the product of two surfaces and from a thick gravitational plane wave sandwiched between two flat spacetimes admit proper curvature collineation in general. The curvature collineation vectors have been determined explicitly. For the space-time formed from the product of two surfaces conditions are obtained for it to admit motion. It has also been pointed out that the spacetime formed from a thick plane gravitational wave belongs to the class (III_b) of pure gravitational radiation and admits five- and six-parameter groups of motion in the two possible cases. Conservation laws given by Sachs and Katzin-Levine-Davis in terms of curvature collineation vectors are satisfied identically in the case of the plane gravitational wave solution, and Sachs' conservation law can be deduced in this case as a consequence of the theorem given by Katzin and others.