Interferometric and Lensing Signatures of Fixed-Ambient Normal-Graph Waves: Linear Scalar Tides, Conformal Null-Path Silence, and Quadratic Disformal Bending

This paper opens the VGM Empirical Correspondence, Calibration, and Falsification series by examining the interferometric and lensing responses of fixed-ambient normal-graph waves. For the exact induced metric on a four-dimensional de Sitter reference embedding, the first metric variation is conformal, whereas the leading nonconformal optical contribution is quadratic in the normal displacement. In the local detector regime, the linear tidal response is scalar: a massless mode produces transverse breathing, while a massive mode has a constrained breathing–longitudinal mixture. The ideal long-wavelength Michelson response and its angular and common-mode nulls are derived. Unparameterized null paths and calibrated conformal shape observables remain unchanged at first order. At quadratic order, the analysis distinguishes coordinate acceleration from physical optical distortion: a single plane profile is pure gauge in the local flat optical limit, whereas two distinct on-shell components generate a nonzero Weyl screen tide and normalized Jacobi shear under a specified vertex-bundle protocol. The resulting conditional hierarchy connects linear timelike tidal response with quadratic null-shape response. Coupling assumptions, approximation limits, calibration requirements, and falsification conditions are stated explicitly. No observational detection, data fit, or empirical validation is claimed.