Chiral dynamics and nuclear matter

✍ Scribed by N. Kaiser; S. Fritsch; W. Weise

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 216 KB
• Volume: 697
• Category: Article
• ISSN: 0375-9474
• DOI: 10.1016/s0375-9474(01)01231-3

✦ Synopsis

We calculate the equation of state of isospin-symmetric nuclear matter in the three-loop approximation of chiral perturbation theory. The contributions to the energy per particle E(k f ) from one-and two-pion exchange diagrams are ordered in powers of the Fermi momentum k f (modulo functions of k f /m π ). It is demonstrated that, already at order O(k 4 f ), two-pion exchange produces realistic nuclear binding. The underlying saturation mechanism is surprisingly simple (in the chiral limit), namely the combination of an attractive k 3 f -term and a repulsive k 4 f -term. The empirical saturation point and the nuclear compressibility K 250 MeV are well reproduced at order O(k 5 f ) with a momentum cut-off of Λ 0.65 GeV which parameterizes short-range dynamics. No further short-distance terms are required in our calculation of nuclear matter. In the same framework we calculate the density-dependent asymmetry energy and find A 0 34 MeV at the saturation point, in good agreement with the empirical value. The pure neutron matter equation of state is also in fair qualitative agreement with sophisticated many-body calculations and a resummation result of effective field theory, but only for low neutron densities ρ n < 0.25 fm -3 .