The Holographic Boundary Principle: A Geometric Normalization from Stellar Photospheres to the Cosmic Horizon

Astrophysical observations probe radiative decoupling surfaces rather than continuous three-dimensional volumes. Treating these surfaces as operational boundaries, we couple directly measured radiative observables with Newtonian surface gravity to define a dimensionless boundary relation. Under standard macroscopic closure, the relation reduces to a mass-independent geometric limit . An independent solar evaluation and a benchmark sample of 190 detached eclipsing binaries show stellar photospheres clustering tightly below this limit with small dispersion. Interpreting radiative decoupling as a geometric boundary condition allows a scale-consistent projection from stellar surfaces to cosmological horizons, yielding constraints in the – plane consistent with Planck measurements. The results indicate that radiative–gravitational systems admit a common boundary normalization across scales, from stellar photospheres to the cosmic horizon.