LORENTZIAN MANIFOLDS ADMITTING ISOTROPIC HYPERSURFACES SOLUTIONS OF EINSTEIN’S FIELD EQUATIONS

Abstract

All spaces solutions of Einstein’s field equations, admitting an isotropic (null) hypersurface (hereafter referred under the acronymus “ishyps”) are determined in a geometric way. We consider in more details two sub-cases, the generalized Robinson-Bertotti, and the pp-waves spaces.