The methods of statistical dynamics are applied to a fluid with 5 conserved
fields (the mass, the energy, and the three components of momentum) moving in a
given external potential. When the potential is zero, we recover a previously
derived system of parabolic differential equations, called "corrections to
fluid dynamics".Comment: extends results of math-ph/0105013 in the presence of an external
field; to appear in Rep. Math. Phys. (2002