Dual-Effect Geometric Mechanism of Wave Function Orthogonality Protection in Five-Dimensional Warped Geometry: Photon-Gravity Decoupling and Phantom Field Stability

This paper constructs a simplified effective model of double scalar fields plus photon in a five-dimensional AdS₅ warped domain wall geometry, and proposes the geometric protection principle of wave function orthogonality: the warped structure of the domain wall determines whether effective interactions can occur between different fields by controlling the distribution of their wave functions along the fifth dimension. This principle simultaneously produces two key physical effects: (1) Photon blinding mechanism — the photon zero-mode wave function is constant along the fifth dimension, and its bilinear overlap integral with the fluctuation of the gravitational scalar mode (N-field) is strictly zero, thereby protecting the electromagnetic force from fifth-force constraints; (2) Ghost blinding mechanism — the wave function of the ghost particle excitation state of the phantom field is exponentially suppressed at the domain wall center, and its trilinear vertex integral with the localized χ-field approaches zero, thereby protecting the phantom field from vacuum decay. Rigorous calculations show that the vacuum decay lifetime is approximately 3.8 × 10⁷ times the age of the Universe, and the five-dimensional domain wall geometry naturally avoids the classical Big Rip singularity through the finite interval and vacuum cutoff. Based on this principle, this paper presents three independently testable quantitative predictions: (i) The dark energy equation of state w(z) crosses w = −1 at redshift zt ≈ 0.3–0.5, in quantitative agreement with DESI 2024 observational data; (ii) The stochastic gravitational wave background produced by domain wall annihilation exhibits a characteristic flat spectrum in the nanohertz band, consistent with NANOGrav 15-year data; (iii) The orthogonal phase relationship between the N-field and χ-field (strictly protected by SO(2) symmetry) leads to a π/2 phase difference in the oscillations of fundamental constants, forming a unique elliptical trajectory in phase space. This model does not attempt to fully embed Standard Model fermions, electroweak unification, or supergravity microscopic ultraviolet completeness; these extensions are left for future work.