A Poincar\'e-covariant study of strange quark stars

TL;DR

This study models strange quark stars using a Poincaré-covariant contact interaction framework, analyzing how model parameters affect the equation of state and stellar properties, and matching predictions with astrophysical observations.

Contribution

It introduces a nonperturbative, symmetry-preserving approach to modeling quark matter and stars, systematically exploring parameter effects and aligning results with observational data.

Findings

Reducing the coupling constant stiffens the EOS.

Increasing the ultraviolet cutoff softens the EOS.

Certain parameter sets match astrophysical constraints well.

Abstract

We investigate the properties of dense quark matter and strange quark stars within a nonperturbative, Poincar\'e-covariant framework. Employing a symmetry-preserving vector$\,\otimes\,$vector contact interaction model, we extend the quark gap equation to the regime of zero temperature and finite quark chemical potential. From the resulting momentum-independent quark propagator, we construct the equation of state (EOS) and solve the Tolman-Oppenheimer-Volkoff (TOV) equations to evaluate the mass-radius relations and tidal deformabilities of strange quark stars. We systematically analyze the sensitivity of the EOS and the macroscopic stellar properties to the model parameters, specifically the effective interaction strength and the ultraviolet cutoff. We demonstrate that reducing the coupling constant stiffens the EOS, whereas increasing the ultraviolet cutoff softens it. By confronting our predictions with multi-messenger astrophysical constraints-including pulsar mass measurements and gravitational-wave data-we identify parameter regimes that successfully describe current observations. Specifically, we find that parameter sets with $\alpha_{ir}=0.735\pi$, $\Lambda_{uv}=0.905\,\mathrm{GeV}$ and $\alpha_{ir}=0.588\pi$, $\Lambda_{uv}=0.9955\,\mathrm{GeV}$, alongside a vacuum bag pressure of $B \approx (0.106\,\mathrm{GeV})^4$, yield stellar properties in excellent agreement with empirical constraints.