Band-Power Reconstruction of Primordial Perturbation Spectrum From CMB Anisotropy

The primordial curvature fluctuation spectrum is reconstructed in terms of the cosmic inversion method using the Wilkinson Microwave Anisotropy Probe data of the cosmic microwave background temperature anisotropy. Applying the covariance matrix analysis, the reconstructed spectrum is decomposed into statistically independent band powers. It is found that while statistically significant deviation from a simple power-law spectrum is found for first-year data, no such deviation is found for the three-year data except possibly at one point near the border of the wavenumber domain where accurate reconstruction is possible. This result, however, does not necessarily rule out theories predicting modulations in the power spectrum.