The General Solution of the Eisenhart Equation and Projective Motions of Pseudo-Riemannian Manifolds

The solution of the Eisenhart equation for pseudo-Riemannian manifolds (Mn,g) of arbitrary signature and any dimension is obtained. Thereby, pseudo-Riemannian h-spaces (i.e., spaces admitting nontrivial solutions h ≠ cg of the Eisenhart equation) of all possible types determined by the Segrè characteristic χ of the bilinear form h are found. Necessary and sufficient conditions for the existence of an infinitesimal projective transformation in (Mn,g) are given. The curvature 2-form of a (rigid) h-space of type χ = {r1, …, rk} is calculated and necessary and sufficient conditions for this space to have constant curvature are obtained.