Paper CCLXXXI: A Parameter-Free Minority Quenching Channel for High-Redshift Massive Galaxies — Vortex-Seeded Overmassive Black Holes and a Gudermannian Brane–Bulk Gamma-Ray Signature

Abstract. The rapid quenching of high-redshift massive galaxies — the DSFG→MQ transition reported by Araya-Araya et al. (2026, A&A 707, A305) and there attributed to merger-triggered AGN feedback — is examined within the One-Octonion Brane-Bulk (OOB) framework. We retract an earlier OOB proposal invoking annihilation of a post-merger black hole against a bulk-antimatter region: that mechanism contradicts framework canon (the antimatter sector is QCD-confined at t~10^-5 s and removed from cosmological scales) and cannot reproduce the observed abundance without two tuned parameters. We replace it with a quenching agent the framework supplies: the vortex-seeded overmassive (‘naked’) black hole, whose comoving abundance is fixed parameter-free by the baryogenesis asymmetry, n_vortex = (δM/M)²·n_Kibble ≈ 2.2×10^-7 Mpc^-3. Against the observed massive-quiescent density n_MQ ~ 10^-5 Mpc^-3, this predicts a minority channel: vortex quenching accounts for ~2–22% of high-z massive quiescent galaxies — the rare M_BH/M_★ > 2 naked-BH subset (confirmed in Abell 2744-QSO1, Juodžbalis et al. 2026) — and not the bulk transition. The pion-decay γ-ray signature is derived through the brane–bulk Gudermannian bridge (gd(∞)=π/2 = the 90° bulk rotation): the bulk coupling fraction is f_bulk(E)=f_III·β_π with f_III=1−4/π²=0.594715, predicting a high-energy plateau at 59.5% and a coupling knee near 208 MeV. Unified with the Paper-CCLXX brane transit form on a single rapidity axis (the sinc argument E/2m_π is exactly γ/2 = coshψ/2), the framework reproduces the Fermi-LAT 270 MeV feature (the pion at γ=2) and the f_III plateau simultaneously. The first-principles absolute seed mass remains open. Honest scope: the abundance and the γ-plateau are parameter-free; the per-object mass and the quenching efficiency are not.