Year: 2021
Type: dissertation
Abstract: In this dissertation, we clarify hidden supersymmetries and the fermion generation structure in extra dimensional models.Extra dimensional models could solve problems left in the Standard Model (SM) and are promising candidates of beyond the SM.We decompose higher dimensional fields in extra dimensional models into Kaluza-Klein (KK) mode functions, and derive 4D effective theories with an infinite number of 4D fields.In these effective theories, we regard massless 4D fields as the ones in the SM and massive fields correspond to new particles.Although many proposals have been made, we have not obtained the sufficient models which unifiedly explain the mysteries in the SM yet.In extra dimensional models, 4D effective theories greatly depend on a geometry and boundary conditions of extra dimensions.Therefore, to construct phenomenological models with extra dimensions, we should reveal the theoretical structure in extra dimensional models from the viewpoint of a geometry and boundary conditions, and clarify when the SM is realized and what new particles appear in the 4D effective theories.These are the main purposes in this dissertation.Here we focus on the structure of the supersymmetric quantum mechanics (SUSY QM) in the 4D mass spectrum obtained from higher dimensional Dirac fields.We show that the structure of N = 2 SUSY QM exists in any extra dimensional models with Dirac fields, which results from the requirement that the mass terms of 4D spinors should consist of the pair of 4D left and righthanded chiral fields.The supercharge in this SUSY QM relates the KK mode functions for 4D left and right-handed chiral fields and explains the 2-fold degeneracy of them.In addition to this 2-fold degeneracy, more degeneracies generally exist in the 4D mass spectrum due to the degrees of freedom of the extra space.We will reveal the structure of N-extended SUSY QM hidden in these degeneracies, and show that the supercharges relate additionally degenerate KK mode functions.Furthermore, the N = 2 SUSY QM indicates that the number of massless 4D chiral fields is related to the topology in extra dimensions.Then, we study the 5D Dirac fermion on quantum graph to investigate the topology and construct the phenomenological models from the viewpoint of general 1D extra spaces.We clarify the allowed boundary conditions and show that the chiral fermions appear from the topology of the boundary conditions on quantum graph.It is also found that this model could naturally solve the problems of the fermion generation, fermion mass hierarchy, the origin of the flavor mixing and CP-violating phase.vi A.2.5 Dirac equation and Klein-Gordon equation on curved spacetime . . . . . .A.2.6 Curvature for spinors . . . . . . . . . . . .
Authors: Ueba, Inori, 上場, 一慶, ウエバ, イノリ
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7056720357