RMB Cosmology IV: Percent-Level Weak Screening and the Minimal Motion–Space Backreaction in the Late Universe

RMB Cosmology IV presents a precision analysis of the weak-screening limit of the screened motion–space cosmological framework.
The study isolates the smallest dynamically viable RMB backreaction that remains consistent with modern percent-level distance measurements.

Main Results

• Conservative parameter ranges:
  L between 0.015 and 0.021,
  k between 4.5 and 6.5,
  a0 between 0.89 and 0.95.

• Minimal backreaction:
  The effective RMB contribution reaches about 1.8 percent today while keeping the deviation in the Hubble rate below 1 percent across all relevant redshifts.

• Distance-measure consistency:
  Supernova luminosity-distance residuals stay below 0.01 mag
  and BAO transverse and radial distance shifts remain below 1 percent.

• Early-universe preservation:
  The RMB activation is exponentially suppressed at early times, ensuring full consistency with the sound horizon, CMB acoustic scale, and recombination physics of standard cosmology.

Methodology

The analysis solves the implicit Friedmann equation with high numerical precision and tests the predictions against Type Ia supernova and BAO measurements.
Growth, lensing and CMB quantities show sub-percent deviations and do not constrain the weak-screening regime.

Context

RMB Cosmology IV provides the conservative baseline of the screened motion–space programme introduced in RMB Cosmology I–III.
It quantifies the minimal allowed RMB backreaction and establishes a fully falsifiable, percent-level framework for future cosmological tests.

Reproducibility

All numerical inputs, scan grids and output files are included.
The paper uses a structured AI-based reproducibility framework with explicit JSON specifications enabling deterministic and audit-ready computation.