Unified Field Interpretation of Galactic Dynamics in the Absence of Non-Baryonic Dark Matter

This paper presents an alternative interpretative framework for cosmological redshift and large-scale galactic distance modeling. Instead of assuming strictly invariant vacuum light propagation under all cosmic-scale conditions, we explore the theoretical consequences of medium-dependent light velocity behavior within intergalactic space. The model does not violate local relativistic constraints but proposes that large-scale propagation characteristics may introduce cumulative observational effects over cosmological distances. We examine three galactic-scale substitution cases and compare resulting redshift-distance relationships to standard ΛCDM assumptions. The analysis focuses on whether medium-structure interactions or large-scale propagation effects could offer partial explanatory alternatives to dark-energy-based expansion interpretations. The study is theoretical and analytical in nature. No new experimental data are introduced; instead, existing cosmological observations are reinterpreted within an alternative propagation framework. Mathematical derivations and substitution models are presented to stimulate further discussion regarding large-scale cosmological light transport assumptions. This work is intended as a conceptual and analytical contribution aimed at encouraging deeper examination of foundational cosmological modeling principles.