Constraining free parameters of a color superconducting nonlocal Nambu–Jona-Lasinio model using Bayesian analysis of neutron stars mass and radius measurements

Scientific paper - Original scientific paper

• Author: M. Shahrbaf
• Author: S. Antić
• Author: A. Ayriyan
• Author: D. Blaschke
• Author: A. G. Grunfeld
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract (english)

We provide a systematic study of hybrid neutron star equations of state (EOS) consisting of a relativistic density functional for the hadronic phase and a covariant nonlocal Nambu–Jona-Lasinio (nlNJL) model to describe the color superconducting quark matter phase. Changing the values of the two free parameters, the dimensionless vector and diquark coupling strengths 𝜂𝑉 and 𝜂𝐷 results in a set of EOS with varying stiffness and deconfinement onset. The favorable parameters are obtained from a systematic Bayesian analysis for which the multimessenger constraint on the neutron star radius at 14𝑀⊙ and the combined mass-radius constraint for PSR J0740+6620 from NICER experiment are used as the constraints. Additionally, the transition from hadronic matter to deconfined quark matter is constrained to occur above nuclear saturation density. Hybrid stars modeled with these favorable parameters are compatible with the NICER results for the radius of the highest known mass neutron star, PSR J0740+6620. Three new observations interesting for neutron star phenomenology are reported: (i) we show that the constant sound speed (CSS) EOS provides an excellent fit to that of the nlNJL model which implies the squared speed of sound at high densities to be about 0.5 for the optimized parameters; (ii) we give a simple functional form for the mapping between the parameter spaces of these two models valid for the whole range of relevant chemical potentials and (iii) we observe that the special point property of hybrid EOS based on CSS quark matter generalizes to a set of lines consisting of special points when two EOS parameters are varied instead of one. A lower limit for the maximum mass of hybrid stars as a function of the vector coupling strength is obtained.

• Keywords (croatian): Nambu–Jona-Lasinio model; Bayesian analysis; neutron stars mass
• Language: croatian
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Physical Review D
• Numbering: vol. 107, no. 5, 054011
• p-ISSN: 2470-0010
• e-ISSN: 2470-0029
• DOI: https://doi.org/10.1103/PhysRevD.107.054011
• URN:NBN: urn:nbn:hr:217:655776
• Publication: 2023
• Document URL: https://link.aps.org/doi/10.1103/PhysRevD.107.054011
• Type of resource: Text
• Access conditions: Open access
• Public note: © 2023 American Physical Society. Received 7 May 2021; accepted 21 February 2023; published 9 March 2023.
• Created on: 2024-07-25 11:22:44