Nuclear symmetry energy and core-crust transition in neutron stars: a critical study

TL;DR

This paper investigates how the slope of nuclear symmetry energy at saturation density influences the core-crust transition in neutron stars, revealing a generally strong correlation with some model-dependent dispersion.

Contribution

It clarifies the relationship between the symmetry energy slope $L$ and the core-crust transition, providing a detailed analysis across various nuclear models and explaining the weak correlation with transition pressure.

Findings

Transition density correlates with $L$ across models.

Correlation between transition pressure $P_t$ and $L$ is weak.

The role of $K_{sym}$ and $L$ correlation is crucial.

Abstract

The slope of the nuclear symmetry energy at saturation density $L$ is pointed out as a crucial quantity to determine the mass and width of neutron-star crusts. This letter clarifies the relation between $L$ and the core-crust transition. We confirm that the transition density is soundly correlated with $L$ despite differences between models, and we propose a clear understanding of this correlation based on a generalised liquid drop model. Using a large number of nuclear models, we evaluate the dispersion affecting the correlation between the transition pressure $P_t$ and $L$. From a detailed analysis it is shown that this correlation is weak due to a cancellation between different terms. The correlation between the isovector coefficients $K_{\rm sym}$ and $L$ plays a crucial role in this discussion.