QCD phase transitions in the light quark chiral limit

Abstract

We investigate the order of the QCD chiral transition in the limit of vanishing bare up/down quark masses and variations of the bare strange-quark mass $0\le m_{\mathrm{s}}\le \infty$. In this limit and due to universality long range correlations with the quantum numbers of pseudoscalar and scalar mesons may dominate the physics. In order to study the interplay between the microscopic quark and gluon degrees of freedom and the long range correlations we extend a combination of lattice Yang--Mills theory and a (truncated) version of Dyson--Schwinger equations by also taking back-reactions of mesonic degrees of freedom into account. Both this system and the meson backcoupling approach have been studied extensively in the past but this is the first work in a full $(2+1)$-flavor setup. Starting from the physical point, we determine the chiral susceptibilities for decreasing up/down quark masses and find good agreement with both lattice and functional renormalization group results. We then proceed to determine the order of the chiral transition along the left-hand side of the Columbia plot, for chemical potentials in the range $-(30\text{MeV}{)}^2\le {\mu }_q^2\le (30\text{MeV}{)}^2$. We find a second-order phase transition throughout and no trace of a first-order region in the $N_f=3$ corner of the Columbia plot. This result remains unchanged when an additional Goldstone boson due to a restored axial ${\mathrm{U}}_{\mathrm{A}}(1)$ is taken into account.

14 pages, 9 figures, 4 tables; v3: version published in PRD; data for plots in ancillary files

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Cited by in corpus (11)

• The chiral phase transition and the axial anomaly
• Soft modes in hot QCD matter
• The QCD moat regime and its real-time properties
• Anomalous $U(1{)}_A$ couplings and the Columbia plot
• Composite Dark Matter with Forbidden Annihilation
• Spatially oscillating correlation functions in $\left(2+1\right)$-dimensional four-fermion models: The mixing of scalar and vector modes at finite density
• Thermal behavior of effective U_A(1) anomaly couplings in reflection of higher topological sectors
• Dilepton production from moaton quasiparticles
• Chiral symmetry restoration in QC_2D from effective model using the functional renormalization group
• Finite-size effects and scaling properties of chiral and baryon-number fluctuations
• On the nature of the QCD chiral phase transition with imaginary chemical potential