Single-particle potential in a chiral approach to nuclear matter including short-range NN-termsS. Fritsch and N. Kaiser
Physik Department T39, Technische Universität München, D-85747 Garching, Germany email@example.com
(Received: 19 December 2002 / Published online: 15 April 2003)
We extend a recent chiral approach to nuclear matter of Lutz et al. (Phys. Lett. B 474, 7 (2000)) by calculating the underlying (complex-valued) single-particle potential . The potential for a nucleon at the bottom of the Fermi sea, U(0,kf0)= - 20.0 MeV, comes out as much too weakly attractive in this approach. Even more seriously, the total single-particle energy does not rise monotonically with the nucleon momentum p, implying a negative effective nucleon mass at the Fermi surface. Also, the imaginary single-particle potential, W(0,kf0)= 51.1 MeV, is too large. More realistic single-particle properties together with a good nuclear-matter equation of state can be obtained if the short-range contributions of non-pionic origin are treated in mean-field approximation (i.e. if they are not further iterated with -exchange). We also consider the equation of state of pure neutron matter and the asymmetry energy A(kf) in that approach. The downward bending of these quantities above nuclear-matter saturation density seems to be a generic feature of perturbative chiral pion-nucleon dynamics.
12.38.Bx - Perturbative calculations.
21.65.+f - Nuclear matter.
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