The S-Layer Cosmology introduces a thin, non-dynamical spectral layer that modifies gravitational behaviour without invoking particle dark matter. A universal saturation law with a fixed exponent of about 0.5 reproduces key galactic and cluster phenomena, including the baryonic Tully Fisher relation, MOND-like low-acceleration behaviour, cored density profiles, flat rotation curves and cluster lensing amplification. The model generates an effective density profile that transitions naturally from a cored inner region to an isothermal-like regime and an NFW-like outer tail. A relativistic extension preserves covariance and gravitational-wave propagation at light speed. At high densities, the S-layer provides a non-singular collapse mechanism. Cosmological implications include slightly enhanced structure growth, characteristic void-boundary behaviour and specific, testable predictions for CMB lensing. This updated version refines the analytical framework and finalises the breathing-core kernel and the cluster amplification function F(b). © 2025 Ralf Zimmermann — Author retains full copyright.
Zimmermann, Ralf (Thu,) studied this question.