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Abstract:
This work deals with a minimal realization of the type-I seesaw model with only
two right-handed Majorana neutrinos, which is investigated from two perspectives;
bottom-up and top-down. In a data-driven approach, the manifestation of
certain hierarchies in the neutrino Yukawa matrix is analyzed in the context of
realizable approximate two-zero textures. A general method for the investigation
of Yukawa structures is developed and applied to the minimal seesaw model. Besides
a robustness study of the obtained results, theoretical error bars are assigned
to this model's predictions. In a top-down ansatz, a high-energy embedding of
the minimal seesaw model is built that exhibits minimal degrees of freedom. A
minimal SU(5) Froggatt-Nielsen
avor model is chosen and assuming approximate
exchange symmetries in the heavy neutrino sector helps to reduce the model's free
parameter. Demanding consistency with electroweak naturalness and leptogenesis
leads to a most minimal type-I seesaw model, that emerges from a high-energy
theory and predicts at the same time all measured neutrino observables.