Abstract
Based on a complete set of $J = 0$ and $J=1$ spatial isovector correlation functions calculated with $N_F = 2$ domain wall fermions we identify an intermediate temperature regime of $T \sim 220 - 500$ MeV ($1.2T_c$--$2.8T_c$), where chiral symmetry is restored but the correlators are not yet compatible with a simple free quark behavior. More specifically, in the temperature range $T \sim 220 - 500$ MeV we identify a multiplet structure of spatial correlators that suggests emergent $SU(2)_{CS}$ and $SU(4)$ symmetries, which are not symmetries of the free Dirac action. The symmetry breaking effects in this temperature range are less than 5%. Our results indicate that at these temperatures the chromo-magnetic interaction is suppressed and the elementary degrees of freedom are chirally symmetric quarks bound into color-singlet objects by the chromo-electric component of the gluon field. At temperatures between 500 and 660 MeV the emergent $SU(2)_{CS}$ and $SU(4)$ symmetries disappear and one observes a smooth transition to the regime above $T \sim 1$ GeV where only chiral symmetries survive, which are finally compatible with quasi-free quarks.
Highlights
Understanding the physics of strongly coupled matter at high temperature is one of the great open challenges in high energy physics
In previous work [21] we have studied a complete set of J 1⁄4 0 and J 1⁄4 1 isovector correlation functions in the z direction for a system with NF 1⁄4 2 dynamical quarks in simulations with the chirally symmetric domain wall Dirac operator at temperatures up to T ∼ 380 MeV
For the scalar ðPS; SÞ pair we find the restoration of Uð1ÞA symmetry to be heavily dependent on the parameters
Summary
Understanding the physics of strongly coupled matter at high temperature is one of the great open challenges in high energy physics. When increasing the temperature to T ∼ 1 GeV we observe that at very high temperature the SUð2ÞCS and SUð4Þ multiplet structure is washed out and the full QCD meson correlators approach the corresponding correlators constructed with free, noninteracting quarks This indicates that at very high temperature the coupling constant is sufficiently small to describe dynamics of weakly interacting quarks and gluons. We begin our presentation with a summary of the calculation of the spatial correlators for free massless quarks in the continuum This situation is the limiting case that should represent QCD at very high temperatures where, due to asymptotic freedom, the interaction via gluons can be neglected. The fact that on the rhs of (16) appears only the dimensionless combination zω0 1⁄4 πz=β 1⁄4 πzT reflects the absence of any physical scale in the conformal theory of massless noninteracting quarks
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