Restricted Gravity: Lagrangian Formalism and Explicit Solutions

It is well known that, making the Abelian projection of Einstein's theory one can obtain the restricted gravity which is simpler than Einstein's theory but describes the core dynamics of Einstein's gravity. In this paper we present the Lagrangian formalism of the restricted gravity which makes the restricted gravity a self consistent field theory by itself, independent of Einstein's theory. With this we present interesting solutions of the restricted gravity, in particular the gravitational cosmic string, the Bertotti-Robinson spacetime, the axisymmetric pp-wave, and the conformally flat waves with flat wavefront. Moreover, we show that in the restricted gravity the Rosen-Bondi gravitational plane wave could be described by two spin-one Maxwellian potentials. This could play important role in quantum gravity. We discuss the physical implications of the restricted gravity.