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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.