Three Further Predictions of the G2 Framework: The Neutron-Proton Mass Difference, Proton Decay, and a Kaluza-Klein Gravitational-Wave Spectrum

We collect three further predictions of the G2 algebraic framework that are individually concise but each testable. First, the neutron-proton mass difference: the framework's quark masses give m_n − m_p = 1.252 MeV against the observed 1.293 MeV (3.2%), with the sign and scale correct before the electromagnetic contribution is fully included. Second, proton decay: with M_GUT = 2 × 10¹ GeV and the framework's ⁶ coupling, the lifetime is _p ≈ 8 × 10³ years — above the current Super-Kamiokande bound and within τ ⁶ the reach of Hyper-Kamiokande in the 2030s. Third, a Kaluza-Klein gravitational-wave spectrum: the two compactification scales of the G2 manifold, whose radius ratio is R /R = 50 = val(N), predict a specific ₂ ₁ ratio in the spacing of Kaluza-Klein graviton modes. We present these together because each is too compact for a separate paper but each adds a falsifiable handle on the framework. We state the maturity of each honestly: the mass difference is a good order-level result pending the full electromagnetic correction, the proton lifetime is an order-of-magnitude estimate within a calculable factor, and the gravitational-wave spectrum is a structural prediction whose absolute frequencies depend on the stillopen compactification scale. Keywords: neutron-proton mass difference, proton decay, grand unification, Kaluza-Klein modes, gravitational waves, G2 compactification, Hyper-Kamiokande