On the nature of the quantum chromodynamics phase transition in hybrid compact stars

Abstract

In this contribution, we study the nature of the quantum chromodynamics (QCD) phase transition in hybrid compact stars. In our approach, we consider a microscopic hadron-quark hybrid equation of state (EoS) to describe the structure of compact stars composed of a quark core and a hadronic shell assuming a structural first-order phase transition at their interface. Our primary purpose in this contribution is to delineate, for a hybrid compact star, the relevant ingredients of their EoSs that simultaneously have the required stiffness and satisfy the constraints of thermodynamics (stability conditions on the free energy, accordance with the laws of thermodynamics and Gibbs' criteria for phase equilibrium). The quark matter structural description is based on the standard MIT bag model, and for the hadron phase modeling, we consider a statistical model for the EoS, which consists of an ensemble of interacting nucleons in statistical equilibrium. In the calculations, the relativistic mean field approximation is used, and the parameters of the approach are taken from experimental data and from nuclear structure calculations. Moreover, exclusion volume effects are implemented in a thermodynamically consistent way so that the transition to uniform nuclear matter can be described in a physically coherent way. We investigate the implications on the structure of a compact hybrid star of considering a Bag constant dependence on the nuclear density, as well as subsidiary aspects of the nature of QCD phase transition as the Gibbs and Maxwell construction realizations of the first-order deconfinement phase transition inside a compact star and observational signals. K E Y W O R D Shybrid star, mean field theory, neutron star, nuclear force