The M-Dwarf Metallicity Cliff and the 21 µm Supernova Dust: Dual Signatures of Dark Nucleosynthesis in a Quantum-Hydrogenic (H₆-FDC) Universe

This paper presents a unified solution to two major astrophysical anomalies: the severe 'M-dwarf metallicity cliff' and the rapid 21 µm 'supernova dust' feature. We propose both are signatures of 'dark nucleosynthesis'—a pre-stellar, geometric element-formation process within dark matter filaments of a quantum-hydrogenic (H₆-FDC) universe. The universe's most abundant stars (M-dwarfs) are missing their low-metallicity ancestors, while supernova ejecta glow with inexplicable 21 µm 'dust.' This work argues these are not separate puzzles, but forensic clues pointing to a flawed foundation. We introduce the H₆-FDC framework, where dark matter is a structured quantum-hydrogenic medium that pre-enriches the cosmos via 'dark nucleosynthesis,' setting a metallicity floor and producing silicate 'brane-ash' visible as the 21 µm feature. The model makes stark, falsifiable predictions, including a direct correlation between the 21 µm feature and dark matter density. Testable predictions are provided. *Version 2 corrected a citation error, Dec. 30, 2025. **Version 3 has an added section with a Testable experimental design: 7.1 “Forged Prototype”: An Executable Testing Scheme, Feb. 6, 2026.