Coupled-cluster calculation for nuclear matter and comparison with the hole-line expansion

The Bochum truncation of the coupled-cluster equations is applied to the nuclear matter problem. Numerical solutions are obtained on the two- and three-particle levels. Approximate treatments for the four-particle level including the four-particle cluster term result in only small contributions, demonstrating the fast convergence of the coupled-cluster scheme. The results are in agreement with variational and hole-line expansion calculations.