EAPSI: Toward Cosmic Expansion in the Framework of Supergravity Theory

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Due to the attractive nature of gravitational interaction, one would expect that our universe is expanding at a decreasing rate. Nevertheless, observations have shown that our universe is undergoing accelerating expansion at present era, and there is much evidence to indicate that a much more rapid expansion occurred in the primordial universe. Even though many phenomenological models have been proposed, the physical origin behind these mechanism is yet unknown. In particular, what kind of particles is responsible for the expansion? Is it possible to accommodate these particles with all other particles that have been discovered so far under a unified theoretical framework? With Prof. Hitoshi Murayama, a leading expert on supersymmetry, supergravity and particle physics cosmology, and with other potential collaborators at Kavli Institute for the Physics and Mathematics of the Universe at Tokyo, Japan, the awardee will attempt to extend our understanding of these fundamental questions under the theoretical framework of supersymmetry, which is a potential candidate that can unify all known interactions in particle physics.The accelerating expansion of our universe at current the era is often attributed to an exotic form of particle/field called dark energy. From the phenomenology point of view, a scalar field with a sufficiently flat potential, named quintessence, could describe dark energy. In this project we aim to construct a quintessence dark energy model that couples to the supersymmetric Standard Model of particle physics, in the framework of supergravity. When combining quintessence model with supersymmetric model of particle physics, generically the flat potential of the quintessence will be spoiled by the supersymmetry breaking. We therefore consider a form of Kahler potential that sequesters the particle physics and quintessence sector, inspired by the brane-world scenario. We will then attempt to build a model based on this and investigate various observational constraints. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Japan Society for the Promotion of Science.