Open and closed CDM isocurvature models contrasted with the CMB data

Abstract

We consider pure isocurvature cold dark matter models in the case of open and closed universe. We allow for a large spectral tilt and scan the 6-dimensional parameter space for the best fit to the COBE, Boomerang, and Maxima-1 data. Taking into account constraints from large-scale structure and big bang nucleosynthesis, we find a best fit with ${\chi }^2=121$, which is to be compared to ${\chi }^2=44$ of a flat adiabatic reference model. Hence the current data strongly disfavour pure isocurvature perturbations.

Comments: 6 pages, 6 figures. V2: Added a discussion of the effect of curvature scale on the primordial power spectrum and made minor changes to match better the Phys. Rev. D 65, 0230XX (2002)