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

A conventional explanation of the dipole anisotropy of the cosmic microwave background radiation is in terms of the Doppler effect: our Galaxy is moving with respect to the cosmic microwave background frame with 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 as 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 investigated. A possible alternative might be a cosmological entropy gradient, as suggested by Paczynski and Piran (1990). We find that contrary to that suggestion a quadrupole anisotropy is generically of the same order of magnitude as the dipole anisotropy (or larger) not only for adiabatic but also for isocurvature initial perturbations. Hence, the observed dipole cannot be explained with a very large scale perturbation which was initially isocurvature.