The Impact of Isospin Asymmetry on Nuclear Matter Properties and its Implications for Neutron Star Equations of State
Abstract
The study of isospin asymmetry in nuclear matter is crucial for understanding the behavior of neutron-rich systems, the nuclear equation of state (EoS), and the structure of neutron stars. This research investigates the impact of isospin asymmetry on binding energy, symmetry energy, nucleon effective mass, and neutron star properties using a combination of Relativistic Mean-Field (RMF), Skyrme-Hartree-Fock (SHF), Brueckner-Hartree-Fock (BHF), and Quantum Monte Carlo (QMC) models. The theoretical predictions were validated using experimental data from heavy-ion collisions and observational constraints from NICER and LIGO-Virgo.
Our results indicate that binding energy per nucleon decreases with increasing isospin asymmetry, with values dropping from -16.0 MeV at α = 0.0 to -8.5 MeV at α = 0.8. The nuclear equation of state (EoS) softens with increasing asymmetry, with pressure at 3.0n0 (saturation density) decreasing from 186.5 MeV/fm³ for symmetric matter to 130.3 MeV/fm³ at α = 0.6. The symmetry energy increases with density, reaching 53.6 MeV at 3.0n0, while the slope parameter (L) is calculated to be 58.7 MeV at saturation, consistent with experimental constraints. Additionally, the neutron effective mass increases while proton effective mass decreases, influencing transport properties in neutron stars.
For neutron star structure, our computed mass-radius relationship aligns with observational data, predicting a maximum neutron star mass of 2.14 ± 0.03M⊙, consistent with PSR J0740+6620. The computed tidal deformability values match LIGO-Virgo constraints from GW170817, validating the nuclear models used.
These findings provide new insights into isospin-dependent nuclear interactions and neutron star physics, with implications for gravitational wave astrophysics, pulsar evolution, and heavy-ion collision experiments. Future work should focus on improving theoretical models, incorporating relativistic corrections, and refining experimental constraints to further bridge the gap between nuclear physics and astrophysical observations.
