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Nonlocal PNJL models and heavy hybrid stars

Nonlocal PNJL models allow for a detailed description of chiral quark dynamics with running quark masses and wave function renormalization in accordance with lattice QCD (LQCD) in vacuum. Their generalization to finite temperature T and chemical potential m allows to reproduce the m-dependence of the pseudocritical temperature from LQCD when a nonvanishing vector meson coupling is adjusted. This restricts the region for the critical endpoint in the QCD phase diagram and stiffens the quark matter equation of state (EoS). It is demonstrated that the construction of a hybrid EoS for compact star applications within a two-phase approach employing the nonlocal PNJL EoS and an advanced hadronic EoS leads to the masquerade problem. A density dependence of the vector meson coupling is suggested as a possible solution which can be adjusted in a suitable way to describe hybrid stars with a maximum mass in excess of 2 M⊙ with a possible early onset of quark deconfinement even in the cores of typical (M ∼ 1.4 M⊙) neutron stars.

compact stars; QCD phase diagram; quark models

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