Compact U (1) lattice gauge theory on the FCC lattice with geometric coupling g² = π²/108. Note added after submission: The one-loop Brillouin zone integral has been computed numerically (2×Π₁ (0) = −0. 4769 at N = 256, matching the required −0. 4775 to 0. 12%). See Paper II (DOI: 10. 5281/zenodo. 19469280) for details and the extension to the mass spectrum. Erratum (12 April 2026): The dark energy density formula in Section 8. 3 (rhoLambda = Eₜransverse x rhoPlanck x epsilon², 16% match) is superseded. The finite-size scaling exponent p = 2. 02 is a correct computational result; however, the dark energy density depends on the instanton screening mechanism identified in Paper VI. The revised formula rhoLambda = (Eᵥac/detᵣatio) x hbar c/ (a² LH²) gives 0. 17% accuracy. The genuine zero-parameter prediction is OmegaLambda = 8 pi Eᵥac/ (3 detᵣatio) = 0. 682 (observed: 0. 685, 0. 39%). See Paper VI for details.
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