Paper CCXXXII: Mass-Dependent Gravitational-Wave Birefringence in GWTC-4

Tong et al. (2026, Nature) report evidence of the pair-instability gap in the secondary-mass distribution of GWTC-4 binary black-hole mergers, with a lower edge at 45+5 -4 M⊙ and an upper edge at 116+9 -13 M⊙. The gap is absent in the primary-mass distribution; four events (GW190519₁53544, GW190602₁75927, GW191109₀10717, GW231102₀71736) have primary components inside the gap with ln ℬ > 8 for the second-generation (2G) hierarchical-merger interpretation. We argue that this subpopulation is the predicted high-birefringence cohort of Prediction P50 (Paper CXXIII) of the One-Octonion Brane-Bulk Framework: hierarchical-merger remnants carry larger T2* coherence radii rT2* = √ (GM/a0) and therefore accumulate larger gravitomagnetic-birefringence phase shifts Δφ ∝ rT2*·f ∝ √M·f across the hyperbolic κ = -1 zone. We test the M1/2 scaling against the 3-OGC parity-violating posteriors of Wang et al. (2022). After controlling for the strong selection-induced mass-distance correlation in the catalog (ρ = 0. 83), we find α (M) = 0. 63 ± 0. 22 and β (d) = 0. 92 ± 0. 17 (R2 = 0. 80, n = 55), consistent with the predicted √M·d scaling at <0. 5σ and rejecting the M2 heuristic of P50 §5 at approximately 6σ. Two of the four Tong 2G candidates (GW190519₁53544, GW190602₁75927) are present in 3-OGC and sit at the top of the |aμ| distribution as predicted. We issue zero-free-parameter forward predictions for GW191109₀10717, GW231102₀71736, and GW231123 (the most massive GWTC-4 event), and correct an inconsistency in P50 §5 by replacing RS with rT2* as the coherence length over which the (+, ×) polarization eigenstates accumulate phase. Part of the One-Octonion Brane-Bulk Framework series. Anchor DOI: 10. 5281/zenodo. 19120873. Community: one-octonion-brane-bulk. Author: Bharathi Dasan Jagadeesan, M. D. , University of Minnesota. ORCID: 0000-0002-1143-941X.