<P> In general relativity, the curvature of spacetime is expressed by the Einstein tensor in the Einstein field equations . </P> <P> These tensor equations determine how spacetime (represented by a manifold) is warped by the presence of mass - energy (expressed in the stress energy tensor), producing the apparent phenomenon of gravitation as a fictitious force . The curvature is highly significant in cosmology, as the shape of the universe affects its ultimate fate . </P> <P> Other hypotheses such as Kaluza - Klein theory and string theory involve a curved spacetime, extended into higher dimensions, in attempts to unify forces as a single phenomenon . </P>

What is another name for the curvature of space-time