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Register a new userA Study of Meson Correlators at Finite Temperature
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We present results for mesonic propagators in temporal and spatial directions at T below and above the deconfining transition in quenched QCD. Anisotropic lattices are used to get enough information in the temporal direction. We use the Wilson fermion action for light quarks and Fermilab action for heavy quarks.
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We consider weakly-coupled QFT in AdS at finite temperature. We compute the holographic thermal two-point function of scalar operators in the boundary theory. We present analytic expressions for leading corrections due to local quartic interactions in the bulk, with an arbitrary number of derivatives and for any number of spacetime dimensions. The solutions are fixed by judiciously picking an ansatz and imposing consistency conditions. The conditions include analyticity properties, consistency with the operator product expansion, and the Kubo-Martin-Schwinger condition. For the case without any derivatives we show agreement with an explicit diagrammatic computation. The structure of the answer is suggestive of a thermal Mellin amplitude. Additionally, we derive a simple dispersion relation for thermal two-point functions which reconstructs the function from its discontinuity.
We report on the results of our calculation of meson correlators in a finite volume. The calculation is carried out in the quenched approximation near the chiral limit (down to Mq = 2.6 MeV) using the overlap fermion. For these small quark masses, the scalar and pseudo-scalar correlators are well approximated with a few hundred eigenmodes. The results for both connected and disconnected correlators are compared with the theoretical predictions of quenched chiral perturbation theory.
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.
We report on the first study of the screening properties of the mesonic excitations with strange ($s$) and charm ($c$) quarks, specifically the ground states of the pseudo-scalar and vector meson excitations for the $bar{s}s$, $bar{s}c$ and $bar{c}c$ flavor combinations, using the Highly Improved Staggered Quark action with dynamical physical strange quark and nearly-physical up and down quarks. By comparing with their respective vacuum meson masses and by investigating the influence of the changing temporal boundary conditions of the valence quarks we study the thermal modifications of these mesonic excitations. While the $bar{s}s$ states show significant modifications even below the chiral crossover temperature $T_c$, the modifications of the open-charm and charmonium like states become visible only for temperatures $Tgtrsim T_c$ and $Tgtrsim1.2T_c$, respectively.
The gluon propagator is investigated at finite temperature via lattice simulations. In particular, we discuss its interpretation as a massive-type bosonic propagator. Moreover, we compute the corresponding spectral density and study the violation of spectral positivity. Finally, we explore the dependence of the gluon propagator on the phase of the Polyakov loop.
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