Unary Field Theory: The Scalar Field Mass at the LIGO Bound

The Unary Field Theory (UFT) predicts a scalar gravitational wave mode with effective mass m_φ = 1.1 × 10⁻²² eV, which lies just below the current LIGO/Virgo graviton mass bound of mg < 1.2 × 10⁻²² eV (90% CL, from GW170817). This proximity is not fine-tuning but a consequence of the UFT's unified structure: the same m_φ governs dark matter phenomenology (galactic rotation curves, soliton core Rₛₒₗ=1.46 kpc), weak lensing (₀=3608), 21-cm cosmology (kJ=1.34 Mpc⁻¹), and scalar GW dispersion. The scalar mode follows a massive scalar dispersion relation vg/c - 1 ∝ 1/f², distinct from massive spin-2 gravitons. Future improvements from LIGO O4/O5 (bound ~ 5×10⁻²³ eV), Einstein Telescope/Cosmic Explorer (bound ~ 10⁻²⁴ eV), and LISA multi-band observations will definitively test the UFT: a null result rules out the theory at >10σ, while a detection confirms cross-scale consistency. This is UFT Prediction Paper XIX; the unified framework is in the main paper: Zou (2026), doi:10.5281/zenodo.21186809.