COSMOLOGICAL CMBR DIPOLE IN OPEN UNIVERSES

The observed cosmic microwave background radiation (CMBR) dipole is ge nerally interpreted as a Doppler effect arising from the motion of the Earth relative to the CMBR frame. An alternative interpretation, prop osed in the last years, is that the dipole results from ultralarge sca le isocurvature perturbations. We examine this idea in the context of open cosmologies and show that the isocurvature interpretation is nor valid in an open universe, unless it is extremely close to a flat univ erse, \Omega(0)-1\less than or similar to 10(-4).