SUGRA, or SUper GRAvity, was discovered in 1976 by Dan Freedman, Sergio Ferrara and Peter Van Nieuwenhuizen. In theoretical physics, supergravity (supergravity theory) is a field theory that combines the principles of supersymmetry and general relativity. Together, these imply that, in supergravity, the supersymmetry is a local symmetry (in contrast to non-gravitational supersymmetric theories, such as the Minimal Supersymmetric Standard Model). Since the generators of supersymmetry (SUSY) are convoluted with the Poincaré group to form a super-Poincaré algebra, it can be seen that supergravity follows naturally from supersymmetry.
Like any field theory of gravity, a supergravity theory contains a spin-2 field whose quantum is the graviton. Supersymmetry requires the graviton field to have a superpartner. This field has spin 3/2 and its quantum is the gravitino. The number of gravitino fields is equal to the number of supersymmetries.
The BICEP2 collaboration has recently reported a large tensor fluctuation in the cosmic microwave background, which suggests chaotic inflation models. In this letter, we reconsider the chaotic inflation model in the supergravity. We introduce a non-holomorphic shift-symmetry breaking parameter, which we expect to exist in general, and discuss its effect on the inflaton dynamics. We show that the model predicts a sizable deviation from the original chaotic inflation model and the predicted tensor fluctuation can lie between the BICEP2 result and the upper bound given by the Planck experiment with a small shift-symmetry breaking parameter. The model is characterized by only two parameters, which yields predictability and testability in future experiments.
Cosmic inflation is a natural scenario which not only solves the flatness and the horizon problem, but also explains the large scale structure of the universe and the fluctuation of the cosmic microwave background (CMB) radiation. Precise observations of the CMB begins to reveal nature of inflation. Chaotic inflation models have been studied in the literature, especially in the context of the supergravity theory (SUGRA). In this letter, we reconsider chaotic in ation models in the SUGRA...
No comments:
Post a Comment