Impact of the Nuclear Equation of State on the Stability of Hybrid Neutron Stars

Mateusz Cierniak,Marc Salinas,Niels-Uwe Bastian,Tobias Fischer,Thomas Klähn

doi:10.3390/universe5080186

Mateusz Cierniak, Marc Salinas + Show 3 more

Open Access

https://doi.org/10.3390/universe5080186

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Abstract

We construct a set of equations of state (EoS) of dense and hot matter with a 1st order phase transition from a hadronic system to a deconfined quark matter state. In this two-phase approach, hadrons are described using the relativistic mean field theory with different parametrisations and the deconfined quark phase is modeled using vBag, a bag–type model extended to include vector interactions as well as a simultaneous onset of chiral symmetry restoration and deconfinement. This feature results in a non–trivial connection between the hadron and quark EoS, modifying the quark phase beyond its onset density. We find that this unique property has an impact on the predicted hybrid (quark core) neutron star mass–radius relations.

Highlights

The current state-of-the-art in the description of strongly interacting matter is the theory of Quantum Chromodynamics (QCD)
The interior of neutron stars attains conditions that are presently inaccessible in nuclear physics and heavy-ion collision experiments
These astrophysical objects, together with core-collapse supernovae [14] and binary neutron star mergers [42], enable us to probe the possible existence of exotic phases of dense matter such as the transition from ordinary nuclear matter to the quark–gluon plasma

Summary

Introduction

The current state-of-the-art in the description of strongly interacting matter is the theory of Quantum Chromodynamics (QCD). The chosen hard cutoff scheme reproduces standard NJL model results and allows for describing quarks as a quasi ideal gas of fermions (assuming constant mass equal to the quarks bare mass) shifted by a constant factor (denoted as Bχ, f ), as seen in Figure 1 of [19]. This is similar to the standard tdBag model approach (cf [15]). Taking the vector interaction into account results in a modification of the effective chemical potential μ∗ and pressure as evident from Equations (9) and (14) This term is not included in the standard tdBag model. The impact on the deconfined quark matter is largely dependent on the choice of hadronic EoS and will be explored in the following chapter

The Phase Diagram

Hybrid Neutron Stars

Conclusions