Einstein-Cartan-Dirac equations in the Newman-Penrose formalism

Abstract

We formulate the Einstein-Cartan-Dirac equations in the Newman-Penrose (NP) formalism, thereby presenting a more accurate and explicit analysis of previous such studies. The equations show in a transparent way how the Einstein-Dirac equations are modified by the inclusion of torsion. In particular, the Hehl-Datta equation is presented in NP notation. We then describe a few solutions of the Hehl-Datta equation on Minkowski space-time, and in particular report a solitonic solution which removes the unphysical behavior of the corresponding Dirac solution. The present work serves as a prelude to similar studies for nondegenerate Poincaré gauge gravity.