Model-independent primordial power spectrum from MAXIMA, BOOMERANG, and DASI data

A model-independent determination of the primordial power spectrum of matter density fluctuations could uniquely probe physics of the very early universe and provide powerful constraints on inflationary models. We parameterize the primordial power spectrum A(s)(2)(k) as an arbitrary function and deduce its binned amplitude from the cosmic microwave background (CMB) radiation anisotropy measurements of MAXIMA, BOOMERANG, and DASI. We find that for a at universe with A(s)(2)(k) = 1 (scale-invariant) for scales k < 0.001 h M pc(-1), the primordial power spectrum is marginally consistent with a scale-invariant Harrison-Zeldovich spectrum. However, we deduce a rise in power compared to a scale-invariant power spectrum for 0.001 h Mpc(-1) less than or similar to k less than or similar to 0.01 h Mpc(-1). Our results are consistent with large-scale structure data and seem to suggest that the current observational data allow for the possibility of unusual physics in the very early universe.