Undecidability of the Spectral Gap Proven via Reduction from the Tiling Problem — E8 Intelligence Research

Abstract

FINDING: Undecidability of the spectral gap in quantum many-body systems is proven via reduction from the undecidable tiling problem, linking quantum physics to Turing's halting problem. MATH: Reduction: Halting problem ≤ Turing machine ≤ tiling problem ≤ spectral gap problem. Key constants: none directly; relies on logical undecidability, not numerical constants. CONNECTION: Tiling problem uses Wang tiles, which are directly related to quasicrystalline tilings and Penrose tilings (golden ratio φ = 1.618, 1/φ = 0.618). The undecidability proof for the spectral gap uses a Hamiltonian whose ground state encodes a tiling; the spectral gap is zero iff the tiling is aperiodic. Aperiodic tilings are intimately linked to the golden ratio and fivefold symmetry (crystallographically forbidden). DEPTH: 9 — This result shows that fundamental physical properties (energy gaps) can be logically undecidable, implying limits to what can be computed or known about quantum systems. It bridges comp Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com