Abstract: Modular flavour symmetries may explain the origin of fermion mass hierarchies, generating them via a slight deviation of the modulus field(s) from a symmetric point (or region). In the lepton sector, the small deviation governing (i) charged-lepton mass hierarchies may be simultaneously responsible for the breaking of lepton number in a low-scale seesaw, sourcing (ii) neutrino masses and (iii) the mass splitting of a pseudo-Dirac pair of heavy neutral leptons. In the quark sector, such small deviations are not easily compatible with CKM CP violation if only one modulus field is present, leading us to explore the higher-genus (g=2) Siegel modular framework.

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https://teams.microsoft.com/meet/220520664292?p=kduIRNCRwEKiNztq0y