A relativistic extension of the particle-hole-hole ring-diagram many-body formalism is developed by using the Dirac equation for single-particle motion in the medium. Applying this new formalism, calculations are performed for nuclear matter. The results show that the saturation density is improved and the equation of state becomes softer as compared to corresponding Dirac-Brueckner-Hartree-Fock calculations. Using the Bonn A potential, nuclear matter is predicted to saturate at an energy per nucleon of -15.30 MeV and a density equivalent to a Fermi momentum of 1.38 ${\mathrm{fm}}^{\mathrm{-}1}$, in excellent agreement with empirical information. The compression modulus is 152 MeV at the saturation point.

• Received 12 January 1993

DOI:https://doi.org/10.1103/PhysRevC.47.2661