Adding crust to BPS Skyrme neutron stars

Abstract

The Skyrme model and its generalisations provide a conceptually appealing field-theory basis for the description of nuclear matter and, after its coupling to gravity, also of neutron stars. In particular, a specific Skyrme submodel, the so-called Bogomol'nyi-Prasad-Sommerfield (BPS) Skyrme model, allows both for an exact field-theoretic and a mean-field treatment of neutron stars, as a consequence of its perfect fluid property. A pure BPS Skyrme model description of neutron stars, however, only describes the neutron star core, by construction. Here we consider different possibilities to extrapolate a BPS Skyrme neutron star at high baryon density to a description valid at lower densities. In the exact field-theoretic case, a simple effective description of the neutron star crust can be used, because the exact BPS Skyrme neutron star solutions formally extend to sufficiently low densities. In the mean-field case, on the other hand, the BPS Skyrme neutron star solutions always remain above the nuclear saturation density and, therefore, must be joined to a different nuclear physics equation of state already for the outer core. We study the resulting neutron stars in both cases, facilitating an even more complete comparison between Skyrmionic neutron stars and neutron stars obtained from other approaches, as well as with observations.

Latex, 21 pages, 3 figures; v3: version as accepted in PRD

References in corpus (17)

• Stringent constraints on neutron-star radii from multimessenger observations and nuclear theory
• Constraint on the maximum mass of neutron stars using GW170817 event
• Skyrmions, instantons and holography
• A BPS Skyrme model and baryons at large Nc
• Light Nuclei of Even Mass Number in the Skyrme Model
• Half-Skyrmions, Tensor Forces and Symmetry Energy in Cold Dense Matter
• Light Nuclei as Quantized Skyrmions
• A dynamical $\alpha$-cluster model of ${}^{16}$O
• States of Carbon-12 in the Skyrme Model
• BPS Skyrmions as neutron stars
• Thermodynamics of the BPS Skyrme model
• Generalized Skyrme model with the loosely bound potential
• Towards Skyrmion Stars: Large Baryon Configurations in the Einstein-Skyrme Model
• Near BPS Skyrmions and Restricted Harmonic Maps
• Oxygen-16 Spectrum from Tetrahedral Vibrations and their Rotational Excitations
• Radial vibrations of BPS skyrmions
• Neutron stars within the Skyrme model

Cited by in corpus (2)

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