Speed of sound and specific heat in the QCD plasma: Hydrodynamics, fluctuations, and conformal symmetry

We report the continuum limits of the speed of sound, $C_s$, and the specific heat at constant volume, $C_V$, in quenched QCD at temperatures of $2T_c$ and $3T_c$. At these temperatures, $C_s$ is within 2-$\sigma$ of the ideal gas value, whereas $C_V$ differs significantly from the ideal gas. However, both are compatible with results expected in a theory with conformal symmetry. We investigate effective measures of conformal symmetry in the high temperature phase of QCD.