Isospin dependence of entrainment in superfluid neutron stars in a relativistic model

TL;DR

This study investigates how the isospin dependence affects the entrainment between superfluid neutrons and protons in neutron stars using a relativistic model with meson exchange, revealing significant influence of rho mesons on entrainment.

Contribution

It introduces a relativistic two-fluid model incorporating rho mesons to analyze isospin effects on entrainment in neutron star interiors, highlighting the rho meson's strong influence.

Findings

Entrainment parameter is affected by rho mesons.

Parameter remains constant at the core and decreases at the surface.

Values of the entrainment parameter are within physical limits.

Abstract

We study the entrainment effect between superfluid neutrons and charge neutral fluid (called the proton fluid) which is made of protons and electrons in neutron star interior within the two fluid formalism and using a relativistic model where baryon-baryon interaction is mediated by the exchange of $\sigma$, $\omega$ and $\rho$ mesons. This model of strong interaction also includes scalar self interactions. The entrainment matrix and entrainment parameter are calculated using the parameter sets of Glendenning (GL) and another non-linear (NL3) interaction. The inclusion of $\rho$ mesons strongly influences the entrainment parameter ($\epsilon_{mom}$) in a superfluid neutron star. The entrainment parameter is constant at the core and drops rapidly at the surface. It takes values within the physical range.