A Critical-Proportion Möbius Strip as a Geometric Model for C₃-Symmetric Physics: Topological Phase Transitions, Berry Phase, and Cross-Disciplinary Correspondences

We present a geometric framework (the “F_N” framework) built from the planar development of a Möbius strip with half-integer twist N=1, parameterized by the aspect ratio r = L/w (length over width). We derive a critical proportion r = 4√3 at which the planar development forms a perfect regular hexagon with zero overlap, and show that this point corresponds to the unique aspect ratio at which folding the hexagon produces a perfect tetrahedron with one open face. We identify three topological regimes separated by this critical point and a lower bound r_min = √3 (independently confirmed by Schwartz’s 2023 proof of the Halpern–Weaver conjecture), and derive a closed-form area law A_central/A_ext = (1 − 4√3/r)² that displays the mathematical signature of a continuous (second-order) phase transition. We derive four geometric invariants, including a topologically protected 60° fold angle and a Berry phase I(N) = −π·δN,1 that is numerically identical to the Berry phase of Dirac cones in graphene and has been experimentally observed in optical Möbius-strip microcavities. We additionally derive a complete classification of the configurations produced when the two extreme topological states are superposed by different reference points (base, centroid, or centroid with 180° rotation), identifying a Star of David configuration as a standard hexagram identity, and propose — with an explicit, sequenced research roadmap — a dynamical extension of the framework treating the angular (A7) and a new radial degree of freedom as a coupled A₁⊗E vibrational system, a structure well established in molecular spectroscopy and independently supported by recent (2025/2026) work on spin-wave dynamics in physical Möbius strips. We document extensive, explicitly labeled cross-disciplinary correspondences — with quantum tunneling, topological superconductivity, ATP synthase rotary catalysis, microtubule helicity, neural grid cells, black-hole topological charge, and the algebraic S₃ origin of fermion generations — together with two exploratory numerical analogies (QCD confinement scale, benzene bond length) presented alongside the evidence currently available for each. All results are organized by epistemic status: formally derived and experimentally verified results (Part A) are clearly separated from investigative proposals at varying stages of development (Part B), each marking ground for future research.