Bergman, O. (1956) Scalar field theory as a theory of gravitation, Amer. J. Phys. 24, 39 Bergmann, P. G. (1968) Comments on the scalar-tensor theory, Int
Lorentzian manifold(英语:Lorentzian manifold) with constant positive scalar curvature(英语:scalar curvature). It is the Lorentzian analogue of an n-sphere(英语:n-sphere)