  Dielectric measurements on molecular liquids just above the glass transition
indicate that alpha relaxation is characterized by a generic high-frequency
loss varying as $\omega^{-1/2}$, whereas deviations from this come from one or
more low-lying beta processes [Olsen et al, Phys. Rev. Lett. {\bf 86} (2001)
1271]. Assuming that long-wavelength fluctuations dominate the dynamics, a
model for the dielectric alpha relaxation based on the simplest coupling
between the density and dipole density fields is proposed here. The model,
which is solved in second order perturbation theory in the Gaussian
approximation, reproduces the generic features of alpha relaxation.
