Equation of State of hot and dense QCD: Resummed perturbation theory confronts lattice data

We perform a detailed analysis of the predictions of resummed perturbation theory for the pressure and the second-, fourth-, and sixth-order diagonal quark number susceptibilities in a hot and dense quark-gluon plasma. First, we present an exact one-loop calculation of the equation of state within hard-thermal-loop perturbation theory (HTLpt) and compare it to a previous one-loop HTLpt calculation that employed an expansion in the ratios of thermal masses and the temperature. We find that this expansion converges reasonably fast. We then perform a resummation of the existing four-loop weak coupling expression for the pressure, motivated by dimensional reduction. Finally, we compare the exact one-loop HTLpt and resummed dimensional reduction results with state-of-the-art lattice calculations and a recent mass-expanded three-loop HTLpt calculation.

Transverse momentum diffusion and jet energy loss in non-Abelian plasmas

We consider momentum broadening and energy loss of high momentum partons in a hot non-Abelian plasma due to collisions. We solve the coupled system of Wong-Yang-Mills equations on a lattice in real time, including binary hard elastic collisions among the partons. The collision kernel is constructed such that the total collisional energy loss and momentum broadening are lattice spacing independent. We find that the transport coefficient $hat{q}$ corresponding to transverse momentum broadening receives sizable contributions from a power-law tail in the $p_perp$-distribution of high-momentum partons. We establish the scaling of $hat{q}$ and of $dE/dx$ with density, temperature and energy in the weak-coupling regime. We also estimate the nuclear modification factor $R_{AA}$ due to elastic energy loss of a jet in a classical Yang-Mills field.

The heavy-quark potential in an anisotropic plasma

We determine the hard-loop resummed propagator in an anisotropic QCD plasma in general covariant gauges and define a potential between heavy quarks from the Fourier transform of its static limit. We find that there is stronger attraction on distance scales on the order of the inverse Debye mass for quark pairs aligned along the direction of anisotropy than for transverse alignment.