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Chiral approach to nuclear matter: Role of explicit short-range NN-terms | | S. Fritsch
; N. Kaiser
; | | Date: |
16 Dec 2003 | | Journal: | Eur.Phys.J. A21 (2004) 117-131 | | Subject: | nucl-th | | Abstract: | We extend a recent chiral approach to nuclear matter by including the most general (momentum-independent) NN-contact interaction. Iterating this two-parameter contact-vertex with itself and with one-pion exchange the emerging energy per particle exhausts all terms possible up-to-and-including fourth order in the small momentum expansion. The equation of state of pure neutron matter, $ar E_n(k_n)$, can be reproduced very well up to quite high neutron densities of $
ho_n=0.5fmd$ by adjusting the strength of a repulsive $nn$-contact interaction. Binding and saturation of isospin-symmetric nuclear matter is a generic feature of our perturbative calculation. Fixing the maximum binding energy per particle to $-ar E(k_{f0})= 15.3 $MeV we find that any possible equilibrium density $
ho_0$ lies below $
ho_0^{
m max}=0.191fmd$. The additional constraint from the neutron matter equation of state leads however to a somewhat too low saturation density of $
ho_0 =0.134 fmd$. We also investigate the effects of the NN-contact interaction on the complex single-particle potential $U(p,k_f)+i W(p,k_f)$. We find that the effective nucleon mass at the Fermi-surface is bounded from below by $M^*(k_{f0}) geq 1.4 M$. This property keeps the critical temperature of the liquid-gas phase transition at somewhat too high values $T_c geq 21 $MeV. The downward bending of the asymmetry energy $A(k_f)$ above nuclear matter saturation density is a generic feature of the approximation to fourth order. Altogether, there is within this complete fourth-order calculation no "magic" set of adjustable short-range parameters with which one could reproduce simultaneously and accurately all semi-empirical properties of nuclear matter. | | Source: | arXiv, nucl-th/0312057 | | Services: | Forum | Review | PDF | Favorites | |
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