THE COSMIC MICROWAVE BACKGROUND DIPOLE CANNOT BE THE RESULT OF THE COSMOLOGICAL ENTROPY GRADIENT

A conventional explanation of the dipole anisotropy of the cosmic micr owave background radiation is in terms of the Doppler effect: our Gala xy is moving with respect to the cosmic microwave background frame wit h similar to 600 km s(-1). However, as the deep redshift surveys fail to reveal a convergence of the large-scale flow to zero at distances a s large as d similar to H-1 15,000 km s(-1) (Lauer and Postman 1994), the uniqueness of the conventional interpretation has to be investigat ed. A possible alternative might be a cosmological entropy gradient, a s suggested by Paczynski and Piran (1990). We find that contrary to th at suggestion a quadrupole anisotropy is generically of the same order of magnitude as the dipole anisotropy (or larger) not only for adiaba tic but also for isocurvature initial perturbations. Hence, the observ ed dipole cannot be explained with a very large scale perturbation whi ch was initially isocurvature.