| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
We utilize temperature anisotropies of cosmic microwave background (CMB) to probe the early universe.
(1) We investigate the accuracy of the numerical calculations for time evolution of temperature anisotropies. Making a comparison with three independent codes, we achieve the level of less than 0.2% numerical errors. With the use of this newly build code, we can make a precise determination of various cosmological parameters.
(2) We set a tight constraint on the gravitational constant from the latest WMAP observations since the physical size of the universe at 400,000 years old, which relates to the observed size of temperature patters, is a function of the gravitational constant. We found that the difference of the gravitational constant at 400,000 years and the present epoch has to be less than 5%.
(3) We propose three models for early reionization of the universe which is suggested by WMAP observations. It is known that the standard cold dark matter model can hardly have such early reionization. First one is to introduce a non-Gaussian statistical feature in density fluctuations. The non-Gaussian tail of high density fluctuations can induce early enough structure formation. Secondly, we consider unknown massive particles which emit UV lights during the decay process. This UV lights ionized the intergalactic medium. Finally, we introduce the isocurvature mode in density fluctuations together with the ordinary adiabatic mode. This isocurvature mode solely induces early structure formation.
(4) We expect to have a polarization component in CMB, which is produced by the scattering off photons by electrons. If we look at the direction of a cluster of galaxies, we always can detect CMB through this cluster. However, the polarization changes its direction due to Fraday rotation. From the precise measurements of CMB polarization toward the cluster direction, we found that we can reconstruct cluster magnetic fields.
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