Multiverse-Induced Gravitational Addendum as a Dark-Matter Proxy: Phenomenological Model and Galactic Rotation-Curve Fits

We propose a phenomenological framework in which dark-matter-like effects emerge from long-range gravitational contributions of an N-order multiverse. The model introduces a sheet-like additive potential term, parameterized by Σₙ(z), which becomes relevant at late cosmic times. This modification effectively boosts baryonic dynamics while remaining consistent with standard Big Bang Nucleosynthesis, Solar-System constraints, and preliminary cosmological tests. The paper demonstrates: rotation-curve fits to SPARC data, including direct Newtonian comparisons with residuals, preliminary checks against Planck 2018 TT+TE+EE likelihoods, a compact histogram analysis of reduced χ² values across galaxy samples, and conceptual illustrations of the multiverse geometry. The framework is analytic, falsifiable, and intended to stimulate community discussion as a potential proxy for dark matter. Keywords: dark matter, modified gravity, multiverse, rotation curves, cosmology, SPARC, Planck 2018