MIRROR PRIMORDIAL NUCLEOSYNTHESIS, THE MOLECULAR COOLING CRISIS, AND THE 50:50 STRUCTURAL ORIGIN OF DARK MATTER (XVI v6)

In the FCD-RBv6 pregeometric framework, the dark sector is derived without exotic particles from the nuclear thermodynamics of the CPT-conjugate mirror brane across the AdS₅ bulk regularized at the Compton floor R₀ ≈ 0.6308 fm. Five core physical and cosmological foundations are formalized: (1) The Inverted Primordial Ratio: via the mirror correspondence (visible proton AAB → mirror antineutron BBA; visible neutron ABB → mirror antiproton BAA), the primordial freeze-out p/n ≈ 7:1 compells an inverted mirror population p̄/n̄ ≈ 1:7; (2) Pauli-Blocking of Antineutron Beta Decay: the acute sparsity of low-energy antiproton phase-space suppresses free antineutron decay, preserving a cold, antineutron-dominated bath; (3) Complete Anti-Hydrogen Deficit: mirror nuclear chemistry consumes 100% of available antiprotons into anti-deuterium and anti-tritium intermediates, terminating strictly at 50% anti-Helium-4 (⁴Hē) and 50% free antineutrons (n̄) by mass, with exactly zero mirror hydrogen; (4) The Molecular Cooling Crisis & Jeans Floor: the complete absence of molecular H₂ closes the low-temperature (< 10,000 K) radiative cooling channel, freezing the fragmentation Jeans mass at galactic scales (10⁶–10⁷ M_☉) and naturally resolving the cusp-core, missing satellites, and too-big-to-fail CDM anomalies without parameter tuning; and (5) Microscopic Basis of the 50:50 Partition & BBN Bounds: this 50% diffuse n̄ and 50% compact ⁴Hē composition provides the physical origin for the 4m bulk tension partition into bound (2m_L) and halo (2m_H) dark matter in cluster collisions (Bullet Cluster), while inter-brane thermal asymmetry is strictly bounded by BBN to ε(z) ≤ 6.3%. All gravitational interactions are mediated by isotropic statistical phase-space depletion (dS = 0).