BPS Skyrme neutron stars in generalized gravity

TL;DR

This paper explores neutron stars within a generalized gravity framework using the BPS Skyrme model, revealing unique mass and stiffness properties that could differentiate nuclear matter models.

Contribution

It introduces the coupling of the BPS Skyrme model with the Starobinsky gravity, providing new insights into neutron star properties in this combined setting.

Findings

Surface redshift mass exceeds ADM mass due to high nuclear matter stiffness.

Results show similarities and discrepancies with previous models, highlighting the impact of nuclear matter properties.

The high stiffness of the BPS Skyrme model influences neutron star characteristics significantly.

Abstract

We study the coupling of nuclear matter described by the BPS Skyrme model to generalized gravity. Concretely, we consider the Starobinsky model which provides the leading-order correction to the Einstein-Hilbert action. Static solutions describing neutron stars are found both for the full field theory and for the mean-field approximation. We always consider the full Starobinsky model in the nonperturbative approach, using appropriately generalized shooting methods for the numerical neutron star calculations. Many of our results are similar to previous investigations of neutron stars for the Starobinsky model using other models of nuclear matter, but there are some surprizing discrepancies. The "Newtonian mass" relevant for the surface redshift, e.g., results larger than the ADM mass in our model, in contrast to other investigations. This difference is related to the particularly high stiffness of nuclear matter described by the BPS Skyrme model and offers an interesting possibility to distinguish different models of nuclear matter within generalized gravity.