The Neutrino Sector from the G2 Singlet: Free Mixing and Compressed Masses from a Single Structural Origin

Two features make neutrinos distinct from the charged fermions: they mix almost freely, with large near-maximal angles, where quarks mix only slightly; and their masses are compressed into a mild hierarchy, where the charged fermions span many orders of magnitude. The Standard Model accommodates both as separate inputs. We show that within the G2 framework both follow from one structural fact: neutrinos occupy the G2 singlet, outside the seven-dimensional representation that carries the octonionic three-form. Because the singlet does not carry the three-form, the selection rule that suppresses generation change for fermions in the seven does not act on neutrinos, and their mixing is unconstrained — large and anarchic, as observed. Because the singlet has no root depth, the factor-of-1/42 suppression that produces the steep charged-fermion hierarchy is absent, and neutrino masses are compressed — mildly hierarchical, as observed (the heaviest-to-middle ratio is about six, against two hundred for the charged leptons). One origin, the singlet nature, yields both the free mixing and the compressed masses. We give the argument and the confirmed qualitative predictions, and state honestly that the precise mixing angles and mass ratio require the singlet operator assignments, which are not yet fixed.