Low-momentum NN interactions and all-order summation of ring diagrams of symmetric nuclear matter
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We study the equation of state for symmetric nuclear matter using a ring-diagram approach in which the particle-particle hole-hole (pphh) ring diagrams within a momentum model space of decimation scale I are summed to all orders. The calculation is carried out using the renormalized low-momentum nucleon-nucleon (NN) interaction V low-k, which is obtained from a bare NN potential by integrating out the high-momentum components beyond I. The bare NN potentials of CD-Bonn, Nijmegen, and Idaho have been employed. The choice of I and its influence on the single particle spectrum are discussed. Ring-diagram correlations at intermediate momenta (k 2 fm-1) are found to be particularly important for nuclear saturation, suggesting the necessity of using a sufficiently large decimation scale so that the above momentum region is not integrated out. Using Vlow-k with I 3 fm-1, we perform a ring-diagram computation with the above potentials, which all yield saturation energies E/A and Fermi momenta kF(0) considerably larger than the empirical values. On the other hand, similar computations with the medium-dependent Brown-Rho scaled NN potentials give satisfactory results of E/A- 15 MeV and kF(0)1.4 fm-1. The effect of this medium dependence is well reproduced by an empirical three-body force of the Skyrme type. 2009 The American Physical Society.