Microscopic three-body force for asymmetric nuclear matter

Abstract

Brueckner calculations including a microscopic three-body force have been extended to isospin asymmetric nuclear matter. The effects of the three-body force on the equation of state and on the single-particle properties of nuclear matter are discussed with a view to possible applications in nuclear physics and astrophysics. It is shown that, even in the presence of the three-body force, the empirical parabolic law of the energy per nucleon vs isospin asymmetry $β=(N-Z)/A$ is fulfilled in the whole asymmetry range $0\leβ\le 1$ up to high densities. The three-body force provides a strong enhancement of symmetry energy increasing with the density in good agreement with relativistic approaches. The Lane's assumption that proton and neutron mean fields linearly vary vs the isospin parameter is violated at high density in the presence of the three-body force. Instead the momentum dependence of the mean fields is rather insensitive to three body force which brings about a linear isospin deviation of the neutron and proton effective masses. The isospin effects on multifragmentation events and collective flows in heavy-ion collisions are briefly discussed along with the conditions for direct URCA processes to occur in the neutron-star cooling.