Study of the equation of state for dark energy and distribution of dark matter by gravitational lensing

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After the precise determination of the cosmological parameters by the observation of Cosmic Microwave Background Radiation, the understanding structure formation of the universe is one of the unsolved and important problem in cosmology. It is well known that dark matter plays a decisive role in this formation and gravitational lens is the only method to observe directly the dark matter. Thus the observation of gravitational lens is very important. In this point of view we performed the observational studies of various gravitational lens phenomena and obtained the following results.1.We performed weak lens analysis of the date from the observations of a distant cluster of galaxies using the Prime forcus came of Subaru Telescope. The cluster is regarded to be at the forming stage. According to our analysis, the distribution of dark matter is well correlated with the distribution of galaxies. This result support the prediction of Cold Dark Matter (CDM) Structure formation scenario.2.We ha … More ve performed strong lens analysis based on Hubble space telescope (HST) and weak lens analysis based on Subaru telescope for a nearby cluster of galaxies A 1689, and determined a precise mass distribution. This gives us a precise determination of the mass of the cluster and density profile. The global shape of the obtained profile coincides with the prediction of the CDM scenario, but we found that the concentration of the density in the central region is much larger than the prediction. We have proposed more observation of cluster of galaxies to HST and Subaru, and accepted partially.3.We have discovered a new cluster of galaxies by weak lens analysis in the region of a distant cluster of galaxies. This indicates the power of the lens analysis to discover cluster of galaxies.4.We have studied the back reaction of an inhomogeneous distribution of matter on the expansion of the universe and found that the effect behaves like the positive spatial curvature and does not change to the acceleration of the expansion. Less