Naoteru Gouda

Non-Linear Growth of Cosmological Density Fluctuation and Type of Singularity

Non-linear growth of density fluctuation in one-dimensional self-gravitating system in the expanding universe is investigated. It is found that the Fourier spectrum of density fluctuation obeys a power law in the small-scale when the singularity of density is first formed. The power index of the Fourier spectrum is -1/3 for almost any initial conditions of density perturbations. The power index is determined only by the type of singularity of the density, which is A3 type in accord with the classification in the catastrophe theory. We also found thatthe effect of non-linearity is very large for the growth of density fluctuations compared with the estimate of the growth rate using a linear theory.

Evolution of Gauge-Invariant Cosmological Density Perturbations through Decoupling Era

We carefully investigate the evolution of cosmological density perturbations through decoupling era in the baryon-photon universe by a gauge-invariant method. It is found that previous results on the same problem obtained by working in the synchronous gauge are inaccurate particularly on comoving scales greater than the horizon scale at equal time. Further, the anisotropy of microwave background radiation is estimated and the result is found to be in good agreement with previous works qualitatively but in disagreement by factors of a few. Also, an attempt is made to clarify physical processes which determine the evolution of both baryon and radiation density perturbations during decoupling era and the physical interpretation is discussed.

JASMINE – design and method of data reduction

Japan Astrometry Satellite Mission for Infrared Exploration (JASMINE) aims to construct a map of the Galactic bulge with 10 μ arc sec accuracy. We use z-band CCD for avoiding dust absorption, and observe about 10 × 20 degrees area around the Galactic bulge region. Because the stellar density is very high, each FOVs can be combined with high accuracy. With 5 years observation, we will construct 10 μ arc sec accurate map. In this poster, I will show the observation strategy, design of JASMINE hardware, reduction scheme, and error budget. We also construct simulation software named JASMINE Simulator. We also show the simulation results and design of software.

Large Scale Anisotropy of the CMB in an Open Universe and Constraints on the Models of Galaxy Formation

We derived the formula by which we can calculate any multipole moment of cosmic microwave background anisotropy in an open universe. we also calculate by using this formula the rms quadrupole moment expected in some cosmological models and we restrict the models by comparing the calculated quadrupole moments with the observed upper limit of the quadrupole moment of the cosmic microwave background anisotropy.