Cosmic Acceleration in the Early and Present Universe

Abstract

Cosmic accelerations in the early and present Universe play essentially important roles to determine the evolution, structure, and destiny of the Universe. Therefore, to identify the origins of cosmic accelerations is one of the most ultimate goals of cosmology. In this award talk for the C. N. Yang Award, I introduced my achievements on this mystery. First of all, we gave a natural mechanism to cause chaotic inflation, which is the most natural inflation model but had never been realized in the context of realistic particle physics for almost twenty years. We introduced a Nambu-Goldstone-like shift symmetry, which is now recognized as a key feature to control the Planck-scale physics, and solved the long standing difficulties to realize chaotic inflation. Second, we found a generic relation (now called Suyama-Yamaguchi inequality) between higher order correlations of the curvature perturbations, which is quite useful to identify what fields are actually responsible for the origin of primordial fluctuation. Finally, we mention our proposal (now called k-essence) for the present cosmic acceleration.