In-medium QCD forces at high temperature

We derive the quantum dynamics of heavy quark systems in quark-gluon plasma as open quantum systems. The scatterings of a heavy quark with the hard medium particles give rise to Debye screened QCD force and drag force and its fluctuation. We present a unified quantum description of these in-medium QCD forces at high temperature in the leading-order perturbation on the basis of the influence functional formalism.Comment: 7 pages, no figure, contribution to SCGT12 "KMI-GCOE Workshop on Strong Coupling Gauge Theories in the LHC Perspective", 4-7 Dec. 2012, Nagoya University; typos corrected in version

A new relativistic hydrodynamics code for high-energy heavy-ion collisions

We construct a new Godunov type relativistic hydrodynamics code in Milne coordinates, using a Riemann solver based on the two-shock approximation which is stable under the existence of large shock waves. We check the correctness of the numerical algorithm by comparing numerical calculations and analytical solutions in various problems, such as shock tubes, expansion of matter into the vacuum, the Landau-Khalatnikov solution, and propagation of fluctuations around Bjorken flow and Gubser flow. We investigate the energy and momentum conservation property of our code in a test problem of longitudinal hydrodynamic expansion with an initial condition for high-energy heavy-ion collisions. We also discuss numerical viscosity in the test problems of expansion of matter into the vacuum and conservation properties. Furthermore, we discuss how the numerical stability is affected by the source terms of relativistic numerical hydrodynamics in Milne coordinates.Comment: 20 pages, 16 figure

Drag force near the QCD critical point

We discuss how heavy quark dynamics is affected by the critical fluctuations near the QCD critical point at finite temperature. We find that the heavy quark momentum diffusion constant scales as $\kappa\propto\xi^{z-3-\eta}$. In the model H scenario, which is widely accepted for the critical dynamics, the exponents are known as $z\simeq 3, \eta\sim 0.04$ and the critical singularity of $\kappa$ is not significant if any. In the model B scenario, $z\simeq 4$ and $\kappa\propto \xi$ is singular near the critical point.Comment: 3 page