Geometric Origin of Back-Reaction Positivity in the COCM

The conditional derivation of orbital ellipticity in NT6 reduces to a single open hypothesis: the back-reaction amplitude delta_y > 0. This note investigates whether delta_y > 0 can be derived from the bulk geometry. The central argument is that the tension asymmetry tau_C0 >> tau_Rn breaks the symmetry delta_y -> -delta_y in the effective orbital potential, generating a negative linear term that displaces the equilibrium from delta_y = 0 to delta_y* > 0. Under four explicit geometric hypotheses G1-G4 (distinct from H1-H3 of NT6), the equilibrium satisfies delta_y* > 0. Under G1-G4, the chain delta_y* > 0 -> J > 0 -> e > 0 is grounded in the bulk geometry. The remaining open sub-problem is G3: the stability of the displacement mode (m_eff^2 > 0).