Equation of state for dense nucleon matter

TLDR

The authors compute the equation of state for dense nuclear and neutron matter using five Hamiltonian models, including Argonne v14, Urbana v14, their combinations with Urbana VII, and a density‑dependent Urbana v14 plus three‑nucleon interaction. Microscopic calculations reveal that Hamiltonians incorporating three‑nucleon forces produce stiffer equations of state than two‑nucleon models, while the Argonne v14 + Urbana VII combination shows a softening near twice nuclear density that may indicate a neutral‑pion condensate.

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 ${v}_{14}$ and Urbana ${v}_{14}$ two-nucleon potentials, both alone and with the Urbana VII three-nucleon potential, and the density-dependent Urbana ${v}_{14}$ 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 ${v}_{14}$ 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.