The QCD equation of state and transition at finite temperature

Abstract

We present the latest results for the equation of state and the crossover transition in 2+1 flavor QCD from the HotQCD Collaboration. Bulk thermodynamic quantities - energy density, pressure, entropy density, and the speed of sound - are calculated on lattices with temporal extent $N_t = 8$ in the temperature range 140 < T < 540 MeV. We utilize two improved staggered fermion actions, asqtad and p4, with the mass for the two degenerate light quarks chosen to be $m_{ud} = 0.1 m_s$, corresponding to $m_\pi \approx 220$ MeV for the lightest pion. We also calculate observables that are sensitive to the chiral and deconfing transitions - the light and strange quark number susceptibilities, the chiral condensate, and the renormalized Polyakov loop - finding that deconfinement and chiral symmetry restoration occur in the same narrow temperature interval.