Research on the evolution of the Universe based on high precision data

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This research project was originally planned to make a consistent evolution history of the early Universe which can account for the two new features of the first-year WMAP results, namely, running of spectral index of the curvature perturbations and early star formation which realizes early reionization based on the model of inflation proposed by the head investigator and collaborators. The other purpose of the project was to pursue the cosmological consequences of heavy moduli fields and gravitinos on dark matter formation and the thermal history. While the project itself was put into practice as we originally designed, the three-year WMAP data, which was disclosed during the research period of this project, withdrew their previous claim of early reionization, so that we reorganized the project accordingly. The main research outcomes are listed as follows.1 We discovered parametric amplification of density perturbations in our model of inflation which can result in intermediate mass primordial black hole formation.2 We established a proper formulation of curvature perturbation in the situation where motion of multiple scalar fields determines the trajectory of the inflaton.3 We calculated the constraint on the neutrino mass in the presence of running spectral index and obtained a more stringent bound than before.4 We analyzed modulus decay to gravitinos and their subsequent decay to neutralino dark matter and showed there was a parameter region that realizes the proper dark matter abundance.5 We formulated fate of the oscillating scalar fields using nonequilibrium quantum field theory.6 We proposed a method to reconstruct primordial power spectrum of fluctuations out of the polarization data of the cosmic microwave background radiation.7 We reconstructed primordial power spectrum using both cosmic inversion and maximum-likelihood matrix method.