Hydrodynamic fluctuations from a weakly coupled scalar field
  Studies of non-equilibrium dynamics of cosmological phase transitions may
involve a scalar field interacting weakly with the energy-momentum tensor of a
thermal plasma. At late times, when the scalar field is approaching
equilibrium, it experiences both damping and thermal fluctuations. We show that
thermal fluctuations induce a shear viscosity and a gravitational wave
production rate, and propose that including this tunable contribution may help
in calibrating the measurement of the gravitational wave production rate in
hydrodynamic simulations. Furthermore it may enrich their physical scope,
permitting in particular for a study of the instability of growing bubbles.
