2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/202065We 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 $χ^2 = 121$, which is to be compared to $χ^2 = 44$ of a flat adiabatic reference model. Hence the current data strongly disfavour pure isocurvature perturbations.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)AstrophysicsHigh Energy Physics - Phenomenologytext