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Abstract

In this thesis, we discuss two important problems of the Standard Model of Particle Physics (SM), namely the flavor problem and the reason for the smallness of neutrino masses. The first one might be related to the origin of non-abelian discrete flavor symmetries. We discuss the possibility of obtaining them from an underlying continuous flavor symmetry, i.e. SU(2) or SU(3) through spontaneous symmetry breaking. Moreover, we investigate their possible origin from an orbifold compactification. We discuss all non-abelian discrete symmetries, which can arise from an orbifold T2/ZN. They are A4, S4, D4, D3, and D6. We present the idea of combining the breaking of an orbifold GUT and the flavor symmetry arising from the orbifold. We demonstrate the construction in a 6d SUSY SO(10) x S4. For the second problem, we propose a one-loop neutrino mass model in the left-right symmetric framework. We observe the transmitted hierarchy from the charged lepton masses to the right-handed neutrino masses, which we call Radiative Transmission of Lepton Flavor Hierarchy''. Finally, we study the phenomenological aspects of the model such as lepton flavor violation (LFV), flavor number violation (FNV), and flavor changing neutral currents (FCNCs).