Environmental Damping of Gravitational-Wave Amplitudes from Bulk Propagation

We propose that gravitational waves propagate through an effective higher-dimensional bulk while electromagnetic signals remain confined to a four-dimensional hypersurface. This geometric flux dilution produces a density-dependent luminosity-distance bias, predicting that gravitational-wave distances exceed electromagnetic distances by 5–10% along high-density sightlines. The model preserves arrival-time synchrony with photons, is consistent with GW170817, and offers a falsifiable prediction testable with upcoming LIGO-Virgo-KAGRA standard-siren catalogs.