Moments of inertia of neutron stars in relativistic mean field theory: the role of the isovector scalar channel

TL;DR

This study investigates how the isovector scalar channel in relativistic mean field theory affects neutron star moments of inertia, crustal properties, and implications for pulsar glitches, highlighting the channel's role in softening the EOS.

Contribution

It introduces the DD-MEδ effective interaction with the isovector scalar channel into RMF theory, showing its impact on neutron star properties and crustal dynamics.

Findings

Reduced neutron star maximum mass and radius with DD-MEδ

Lower total and crustal moments of inertia in DD-MEδ

Decreased crustal thickness and mass fraction due to the isovector scalar channel

Abstract

With the inclusion of the isovector scalar channel in the meson-nucleon couplings, taking DD-ME$\delta$ as an effective interaction, the moments of inertia of neutron stars possessing various stellar masses are studied within the density dependent relativistic mean field (RMF) theory. The isovector scalar channel contributes to the softening of the neutron-star matter equation of state (EOS) and therefore the reduction of the maximum mass and radius of neutron stars. Smaller values of the total moment of inertia $I$ and the crustal moment of inertia $\Delta{I}$ are then obtained in DD-ME$\delta$ via numerical procedure in comparison with those in other selected RMF functionals. In addition, the involvement of the isovector scalar channel lowers the thickness of the neutron star crust and its mass fraction as well. The sensitivity to both the crustal mass and stellar radius causes the crustal moment of inertia to be more obviously reduced than the total one, eventually leading to a suppression on the fraction of crustal moment of inertia $\Delta{I}/I$ in DD-ME$\delta$. The results indicate the crustal moment of inertia as a more sensitive probe of the neutron-star matter EOS than the total one, and demonstrate that the isovector scalar meson-nucleon couplings in the RMF theory could exert influence over the physics of pulsar glitches.