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We use the localized principle component analysis to detect deviations from scale invariance of the primordial power spectrum of curvature perturbations. With the technique we make uncorrelated estimates of the primordial power spectrum with five wavenumber bins. In the framework of a minimal LCDM model, using the latest cosmic microwave background data from the WMAP and ACT experiments we find that more than 95% of the preferred models are incompatible with the assumption of scale-invariance, but still compatible with a power-law primordial spectrum. We also forecast the sensitivity and constraints achievable by the Planck experiment by performing Monte Carlo studies on simulated data. Planck could significantly improve the constraints on the primordial power spectrum, especially at small scales by roughly a factor of 4., Comment: 8 pages, 2 figures, 1 table, JCAP style, references added, published version. arXiv admin note: substantial text overlap with arXiv:1105.5916

We investigate the cosmological evolution of the system of a Dirac–Born–Infeld field plus a perfect fluid. We analyze the existence and stability of scaling solutions for the anti-de Sitter throat and the quadratic potential. We find that the scaling solutions exist when the equation of state of the perfect fluid is negative and in the ultra-relativistic limit.