Hybrid Resonant Type-I and Type-II Leptogenesis in SO(10) with Quasi-Degenerate Triplet and Right-Handed Neutrino Masses $M_T\simeq M_{N_3}$

The origin of the baryon asymmetry of the Universe remains one of the central open problems in particle physics and cosmology. We identify a regime of \emph{hybrid resonant leptogenesis} in renormalizable SO(10) grand unified theories, where a quasi-degeneracy between the scalar triplet and the heaviest right-handed neutrino, $M_T\simeq M_{N_3},$ naturally arises from their common origin in unified scalar multiplets and leads to an enhanced interference between type-I and type-II decay amplitudes. This interference gives rise to a physical CP-violating phase, ${\phi }_{\mathrm{H}\mathrm{R}}=\arg (\mu f{Y}_{\nu }^{†}),$ which cannot be removed by field redefinitions and induces a resonant enhancement of the baryon asymmetry without requiring extreme Yukawa hierarchies or fine-tuned mass splittings. We show that the observed asymmetry, $Y_B\simeq 8.7\times {10}^{-11},$ can be reproduced for mass scales around ${10}^{11}\mathrm{G}\mathrm{e}\mathrm{V}$, moderate washout effects, and $\mathcal{O}(1)$ CP-violating phases. The mechanism leads to correlated low-energy signatures in lepton-flavour violation and electric dipole moments, providing potential experimental tests.