Galilean invariance and vertex renormalization in turbulence theory.
The Navier-Stokes equation is invariant under Galilean transformation of the instantaneous velocity field. However, the total velocity transformation is effected by transformation of the mean velocity alone. For a constant mean velocity, the equation of motion for the fluctuating velocity is automatically Galilean invariant in the comoving frame, and vertex renormalization is not constrained by this symmetry.
McComb
W D
WD
School of Physics, University of Edinburgh, UK. w.d.mccomb@ed.ac.uk