Isotropy of the early universe from CMB anisotropies

The acoustic peak in the CMB power spectrum is sensitive to causal processesand cosmological parameters in the early universe up to the time of lastscattering. We provide limits on correlated spatial variations of the peakheight and peak position and interpret these as constraints on the spatialvariation of the cosmological parameters (baryon density, cold dark matterdensity and cosmological constant as well as the amplitude and tilt of theoriginal fluctuations). We utilize recent work of Hansen, Banday and Gorski(HBG) who have studied the spatial isotropy of the power spectrum as measuredby WMAP by performing the power spectrum analysis on smaller patches of thesky. We find that there is no statistically significant correlated asymmetry ofthe peak. HBG have also provided preliminary indications of a preferreddirection in the lower angular momentum range(~ 2-40) and we show how possibleexplanations of this asymmetry are severely constrained by the data on theacoustic peak. Finally we show a possible non-gaussian feature in the data,associated with a difference in the northern and southern galactic hemispheres.Comment: 14 pages, 3 figures, v.2 adds an extra relevant reference and commen