Microscopic Theory of the Nuclear Equation of State and Neutron Star Structure

Abstract

Abstract. The Bethe-Brueckner-Goldstone many-body theory of the Nuclear Equation of State is reviewed in some details. In the theory, one performs an expansion in terms of the Brueckner two-body scattering matrix and an ordering of the corresponding many-body diagrams according to the number of their hole-lines. Recent results are reported, both for symmetric and for pure neutron matter, based on realistic twonucleon interactions. It is shown that there is strong evidence of convergence in the expansion. Once three-body forces are introduced, the phenomenological saturation point is reproduced and the theory is applied to the study of neutron star properties. One finds that in the interior of neutron stars the onset of hyperons strongly softens the Nuclear Equation of State. As a consequence, the maximum mass of neutron stars turns out to be at the lower limit of the present phenomenological observation.

QCD in Neutron Stars and Strange Stars

“…Finally, the density at which quarks deconfine follows from this study to be of the order of five times that of nuclear saturation density, which is well within reach of typical neutron star densities [1,2,3,4,6,7,8,9,10].…”

“…These are white dwarfs, neutron stars, and black holes. Of the three, neutron stars appear particularly interesting for QCD related studies of ultra-dense matter, since the matter in the cores of such objects is compressed to densities that are several times higher than the densities of atomic nuclei [1,2,3,4,5,6,7,8,9,10]. Theoretical studies indicate that at such densities hyperons may be generated and new states of matter-such as boson condensates and/or quark matter-may appear [1,2,3,6].…”

Density-dependent nucleon-nucleon interaction from three-nucleon forces

“…As a final remark, the effective potential discussed in our paper could be easily employed in many-body approaches other than those based on the CBF formalism or quantum Monte Carlo simulations, such as the G-matrix and self-consistent Green function theories [52][53][54].…”

Hot neutron matter from a self-consistent Green's-functions approach

“…In neutron matter, Pauli effects block this tensor channel, but short-range correlations still need to be accounted for appropriately. Several theoretical approaches have been developed over the years to treat these correlations in zero-temperature neutron matter, including variational techniques within correlated basis functions [4][5][6], auxiliary field [7] or quantum Monte Carlo [8] calculations with simplified interactions, and the popular Brueckner-BetheGoldstone hole-line expansion [9] in its lowest order form, the so-called Brueckner-Hartree-Fock (BHF) approximation [10]. At finite temperatures, fewer efforts have been focused in this direction: the well-known variational calculation of Friedman and Pandharipande [11] and recent similar calculations [12], as well as BHF extensions at finite temperature [13,14].…”