Equation of state for dense nucleon matter

Abstract

We report microscopic calculations of the equation of state for dense nuclear and neutron matter. The calculations are performed for five Hamiltonians: the Argonne u && and Urbana v &4 two-nucleon potentials, both alone and with the Urbana VII three-nucleon potential, and the density-dependent Urbana u&4 plus three-nucleon interaction model of Lagaris, Friedman, and Pandharipande. The beta-stable equation of state and neutron star structure are also calculated for three of the models. The models with the three-nucleon potential bracket the density-dependent model and are significantly stiffer than those with an unmodified two-nucleon potential only. The Argonne u&4 plus Urbana VII Hamiltonian produces a softening in the neutron matter equation of state localized around twice nuclear matter density which may indicate a neutral pion condensate.

Cluster formation in asymmetric nuclear matter: Semi-classical and quantal approaches

“…Now, the RPA modes are defined by the condition (30), which can be expressed in a closely related form as:…”

“…Two other Skyrme forces are used for comparison: RATP [27] -the first interaction which includes neutron matter into the fitting procedureand SGII [28], a typical widely used parameterization. The interaction RATP is constrained by the neutron-matter equation of state calculated by Friedman and Pandharipande in the 80ies [29], while the interaction SLy230a uses a more recent neutron-matter equation of state based on an improved realistic interaction [30]. Let us remark that these interactions have quadratic velocity-dependent terms which modify the single-particle energies and give rise to effective masses m * i (i=n, p).…”

Inner edge of neutron-star crust with SLy effective nucleon-nucleon interactions

“…The SLy forces have been constructed as to be consistent with the UV14+UVII model of Wiringa et al [20] of neutron matter above ρ 0 [6,7]. It is therefore of interest to see how well these effective N-N forces reproduce the UV14+UVII model of neutron matter at subnuclear densities.…”

“…Relevant additional experimental items concerning neutron rich nuclei (isovector effective masses), constraints of spin stability, and requirement of consistency with the UV14+VIII equation of state (EOS) of dense neutron matter of Wiringa et al [20] for ρ 0 ≤ ρ ≤ 1.5 fm −3 , were combined with general procedure of fitting the properties of doubly magic nuclei. This procedure led to a set of the SLy (Skyrme Lyon) models, which -due to the emphasis put on their neutron-excess dependence -seem to be particularly suitable for the calculations of the properties of neutron-star crust.…”

The Final Fate of Coalescing Compact Binaries: From Black Hole to Planet Formation

“…Almost independent of the spins of the NS, all hydrodynamic calculations suggest that about 10% of this mass will be ejected into the outer torus, leaving at the center a maximally rotating object with baryonic mass ≃ 2.7 M ⊙ (Any hydrodynamic merger process that leads to mass shedding will produce a maximally rotating object since the system will have ejected just enough mass and angular momentum to reach its new, stable quasiequilibrium state). Most stiff NS EOS (including the well-known "AU" and "UU" EOS of Wiringa et al 1988 For slowly rotating stars, the same stiff NS EOS give maximum stable baryonic masses in the range 2.5 − 3 M ⊙ , which may or may not exceed the total merger core mass. Therefore, collapse to a BH could still occur on a timescale longer than the dynamical timescale, following a significant loss of angular momentum.…”