Slow Electromechanical Interference Links Division Geometry, Differentiation Bias, and Senescence-like Arrest

This work develops a biophysical theory in which a bioelectric field V(x,t) and a cortical stress field sigma(x,t) are weakly and reciprocally coupled. Because the mechanical side is inertial-viscoelastic, the coupled system supports two underdamped normal modes whose interference generates a measurable slow cadence f_slow = (omega_{+,r} - omega_{-,r})/(2pi). Sampling the dynamics at the neutral moment (the recurring near-symmetric crossing between V and sigma) yields an even circle map (mod pi) for the slow phase with effective forcing Omega and even-harmonic coupling K2. Both Omega and K2 are predicted a priori from independently measured electrical (tau_m, D_V, beta_R, beta_I) and mechanical (kappa, eta, rho_eff, D_sigma, gamma) properties, without ad hoc integer fitting. In this picture, helical quantization appears as a phase-locking problem: the canonical B-DNA rotation number ~10.5 corresponds to the high-order lock rho_pi = 2/21, centered at Omega = pi2/21. We define a functional order parameter Lambda as the cross-spectral coherence C_{Vsigma}(f_slow) between V and sigma at f_slow. We hypothesize that healthy epithelia repeatedly re-enter a narrow 2/21 lock each slow cycle, which stabilizes spindle orientation and cortical anchoring and constrains chromatin torsion. Drifting out of that lock suggests two generic failure modes: (i) persistent unlocking with low Lambda and elevated spindle-angle dispersion (dysregulated proliferation and abnormal division geometry), and (ii) aging-like overlock with high coherence but low plasticity. The theory yields three preregisterable, falsifiable predictions: (P1) homeostatic epithelia exhibit a shared slow-band cadence in both V and sigma together with a coherence peak Lambda = C_{Vsigma}(f_slow); (P2) the point (Omega, K2), obtained from directly measured properties plus neutral-moment strobing, lies inside the 2/21 Arnold tongue while avoiding broad low-order tongues; (P3) a weak, frequency-specific electrical or mechanical drive at f_slow increases Lambda and reduces spindle-angle dispersion, whereas an energy-matched off-resonant control does not. We provide analytical bounds, a numerical sandbox, and preregistered analysis code, enabling direct experimental falsification using combined optical electrophysiology and mechanical readouts.