  To study the rate of energy and momentum loss of a heavy quark in QGP,
specifically in the hydrodynamic regime, we use fluid/gravity duality and
construct a perturbative procedure to find the string solution in gravity side.
We show that by this construction the drag force exerted on the quark can be
computed perturbatively, order by order in a boundary derivative expansion. At
ideal order, our result is just the drag force exerted on a moving quark in
thermal plasma with thermodynamics variables promoted to become local functions
of space and time. Furthermore, we apply this procedure to a transverse quark
in Bjorken flow and compute the first-derivative corrections, namely the
viscous corrections, to the drag force.

High Energy Physics - Theory;High Energy Physics - Phenomenology