CDM Discrimination
Strongly SupportedCold Dark Matter (CDM) models predict a specific amount of intrinsic scatter in the Radial Acceleration Relation. The measured scatter from 14,760 galaxies is below that prediction. This constrains — but does not rule out — the CDM framework.
Why Scatter Matters
In CDM cosmology, each galaxy forms inside a dark matter halo with its own assembly history: different merger trees, different concentration parameters, different baryon fractions. This diversity should produce scatter in the RAR. Simulations from the EAGLE, IllustrisTNG, and FIRE projects predict σint ≈ 0.11–0.16 dex from halo-to-halo variation alone.
The observed value of 0.086 ± 0.003 dex is tighter than these predictions. The RAR is “too tight” for a universe where dark matter halos have such diverse histories.
Three Frameworks Compared
CDM (ΛCDM)
Predicted scatter: σint ≈ 0.11–0.16 dex from halo diversity. To match the observed 0.086, CDM must invoke finely-tuned baryonic feedback that somehow erases halo-to-halo variation. Possible, but requires additional physics.
MOND
Predicted scatter: σint ≈ 0 (the RAR should be exact in pure MOND). The observed 0.086 dex comes from observational errors and M/L variations. MOND naturally explains the tightness.
Synchronism
Predicted scatter: small and environment-dependent. The coherence function allows slight variations based on local density, explaining why the scatter is not zero but is much tighter than CDM expects. The environment dependence was confirmed at p = 5 × 10−6.
Sessions #604–610
This analysis was performed across Sessions #604–610 of the autonomous research program. The key methodological steps: (1) bootstrap resampling to estimate σint independent of measurement errors, (2) comparison against published CDM predictions from EAGLE and IllustrisTNG, (3) environment binning to test coherence predictions.
Honest Caveat
This result constrains CDM but does not rule it out. CDM simulations are continuously improving, and baryonic feedback models are getting more sophisticated. It is entirely possible that future CDM simulations with better subgrid physics will reproduce the observed tightness. Additionally, the scatter measurement itself depends on assumptions about distance errors and mass-to-light ratios. The tension is suggestive, not decisive.