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.
Andrew Wright (Wed,) studied this question.