Phase diagram of neutral quark matter in nonlocal chiral quark models

• Autores: Gómez Dumm, Daniel Alberto; Blaschke, David; Grunfeld, Ana Gabriela; Scoccola, Norberto Nerio
• Año de publicación: 2006
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Exactas; Física; phase diagram; Physics; quark matter; neutral quark matter
• Institución: Universidad Nacional de La Plata

We consider the phase diagram of two-flavor quark matter under neutron star constraints for two nonlocal, covariant quark models within the mean-field approximation. In the first case (Model I) the nonlocality arises from the regularization procedure, motivated by the instanton liquid model, whereas in the second one (Model II) a separable approximation of the one-gluon exchange interaction is applied. We find that Model II predicts a larger quark mass gap and a chiral symmetry breaking (CSB) phase transition line which extends 15–20% further into the phase diagram spanned by temperature (T) and chemical potential (μ). The corresponding critical temperature at μ = 0,T_c(0) ≃ 140 MeV, is in better accordance to recent lattice QCD results than the prediction of the standard local NJL model, which exceeds 200 MeV. For both Model I and Model II we have considered various coupling strengths in the scalar diquark channel, showing that different low-temperature quark matter phases can occur at intermediate densities: a normal quark matter (NQM) phase, a two-flavor superconducting (2SC) quark matter phase and a mixed 2SC-NQM phase. Although in most cases there is also a gapless 2SC phase, this occurs in general in a small region at nonzero temperatures, thus its effect should be negligible for compact star applications.
Facultad de Ciencias Exactas
Instituto de Física La Plata