Derivation of fluid dynamics from
the Boltzmann
equation, G.
Denicol, Frankfurt
University, Germany − We
present a general derivation of relativistic fluid dynamics from
the
relativistic Boltzmann equation using the method of moments. The main difference
between our approach and
the traditional 14-moment approximation is that we do not close
the
fluid-dynamical equations of motion by truncating the expansion of
the
distribution function. Instead, we keep all the terms in the
moment expansion
and truncate the exact equations of motion for the moments
according to a
systematic power counting scheme in Knudsen and Reynolds number. We apply this formalism to
obtain an
approximate expression for the non-equilibrium single-particle
momentum
distribution function. This
result is
essential to improve the freeze-out description used in the
fluid-dynamical
modeling of relativistic heavy ion collisions. In order to
investigate the
implications of our new formalism, we compute the distribution
function of a
simple system composed of pions, Kaons and nucleons and compare it
to the one
obtained via the 14-moment approximation.