Supporting the existence of the QCD critical point by compact star observations
David E. Alvarez-Castillo, David Blaschke
备注：
6 pages, prepared for the Proceedings of the Conference "9th International Workshop on Critical Point and Onset of Deconfinement - CPOD2014", 17-21 November 2014, ZiF (Center of Interdisciplinary Research), University of Bielefeld, Germany
In order to prove the existence of a critical end point (CEP) in the QCD phase diagram it is sufficient to demonstrate that at zero temperature $T=0$ a first order phase transition exists as a function of the baryochemical potential $μ$, since it is established knowledge from ab-initio lattice QCD simulations that at $μ=0$ the transition on the temperature axis is a crossover.
We present the argument that the observation of a gap in the mass-radius relationship for compact stars which proves the existence of a so-called third family (aka "mass twins") will imply that the $T=0$ equation of state of compact star matter exhibits a strong first order transition with a latent heat that satisfies $Δε/ε_c \gt 0.6$.
Since such a strong first order transition under compact star conditions will remain first order when going to symmetric matter, the observation of a disconnected branch (third family) of compact stars in the mass-radius diagram proves the existence of a CEP in QCD. For the equation of state of the twins the quark matter description is based on a QCD-motivated chiral approach with higher-order quark interactions in the Dirac scalar and vector coupling channels. For hadronic matter we select a relativistic mean-field equation of state with density-dependent couplings. Since the nucleons are treated in the quasi-particle framework, an excluded volume has been included for the nuclear equation of state at super-saturation density that takes into account the finite size of the nucleons.
Furthermore we show results of a Bayesian analysis (BA) using disjunct M-R constraints for extracting probability measures for cold, dense matter equations of state. This study reveals that measuring the radii of neutron star twins has the potential to support the existence of a first order phase transition for compact star matter.
QCD axions and domain walls in dense matter under compact stellar conditions
Hunan University of Science and Technology（湖南科技大学）；Beihang University（北京航空航天大学）；Fudan University（复旦大学）；University of Catania（卡塔尼亚大学）；Inner Mongolia Normal University（内蒙古师范大学）
