Title: Generalizations of solid inflation
Description: Solid inflation is a unique inflationary model, in which inflatons have time-independent but spatially dependent vacuum expectation values. Since it does not conform to conventional inflationary models, it gives quite unique observational predictions, which in principle can be tested by observations. However, the original version of solid inflation hypothesizes an ideal type of solid: an isotropic solid. As a generalization, this thesis discusses a more realistic solid, which has a symmetry under a point group. As a result, its underlying structure can be maximally anisotropic even though it can still give isotropic predictions at the background and quadratic fluctuations in scalar modes. In another branch of generalizations, this thesis performs a thorough analysis of higher-derivative interactions in solid inflation, which the original version ignores.