Abstract
The mass sensitivity of the chiral phase transition of QCD with and without axial $U_A(1)$-symmetry breaking at vanishing and finite quark chemical potential is investigated. To focus on the low-energy sector of QCD, a quark-meson model with three dynamical quark flavors is employed. Non-perturbative quantum fluctuations are taken into account with the functional renormalization group. The inherent ambiguities in fixing the low-energy model parameters away from the physical mass point and their consequences for spontaneous chiral symmetry breaking are discussed in detail and a heuristic parameter fixing scheme motivated by chiral perturbation theory is proposed. The influence of vacuum and thermal fluctuations of quarks and mesons on the order of the chiral phase transition is additionally assessed with a mean-field analysis.
Highlights
Quantum chromodynamics (QCD) at finite temperature and density predicts a phase transition at low energies from confined hadronic matter to a deconfined quark-gluon plasma
Owing to the scarce information about QCD away from the physical point, we explore two strategies to fix the parameters in this case: (i) Fixed-UV scheme: Away from the physical point only the explicit symmetry breaking sources jl;s are assumed to change, while all other parameters of the initial effective action are identical to the ones at the physical point
In this work we extend the investigation of the chiral phase transition for arbitrary symmetry breaking sources jl and js as well as finite chemical potential
Summary
Quantum chromodynamics (QCD) at finite temperature and density predicts a phase transition at low energies from confined hadronic matter to a deconfined quark-gluon plasma. The nature of the chiral transition in the small mass region of the Columbia plot is still controversial concerning several lattice QCD studies for two and three quark flavors. In optimized perturbation theory and the mean-field treatment of the QM model a large first-order region in the chiral and in the light chiral limit is obtained [51,52] In such studies, the Columbia plot exhibits features which are qualitatively independent of the axial anomaly [53]. It was found that the chiral transition in the light chiral limit at physical strange quark masses is of second order belonging to the Oð4Þ-universality class in the presence of the axial anomaly. Details of our numerical implementation are given in the Appendix
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