Locally Supersymmetric Effective Field Theories of Inflation

Abstract: Supergravity, a locally supersymmetric gauge theory, may provide to describe new physics beyond the Standard Model (BSM). In this sense, cosmological applications of supergravity can be the arena for probing outcomes of supergravity. It is also attractive that supergravity can appear as a low-energy effective theory of superstrings, a possible candidate of quantum gravity. Nevertheless, it is not trivial to build inflationary models in supergravity due to difficulties arising mainly from the extremely constrained form of supergravity scalar potentials, complicated structure of interaction terms, and excessive scalar degrees of freedom. These obstructions generally make it challenging to contrive a desirable inflationary trajectory, perform the moduli stabilization to obtain the stable de-Sitter phase, and make extra scalars to be much heavier than the Hubble scale to get single field inflation. Besides, supergravity predicts many non-renormalizable interactions. It thus arises as effective field theory (EFT) which can be valid only up to typical energies $E$ below its ultraviolet cutoff scale $\Lambda_{cut}$, and up to some accuracy of $(E/\Lambda_{cut})^n$ that we desire. We note that these non-renormalizable terms may affect physics during and/or after inflation. From such points of view, it is very important in supergravity to find the method for relaxing the scalar potentials, and flexible scalar field dynamics (particularly for inflaton), and examine self-consistency at the quantum level. In this thesis, therefore, we construct locally supersymmetric effective field theories of inflation (with KKLT string background) by taking into account recently-proposed reformulations of $\mathcal{N}=1$ supergravity that can enlarge the space of scalar potentials.