Overview
This article presents a phenomenological investigation of two long-standing observational anomalies: flat galaxy rotation curves and the Hubble constant tension. Although usually treated separately, both phenomena probe gravitational inference in low-density environments.
The analysis introduces a minimal effective framework in which the gravitational response saturates below a characteristic scale. The framework is explicitly restricted to late-time phenomenology and does not modify early-universe physics or the global cosmological expansion history.
Core contributions
- Unified phenomenology: rotation curves and Hubble tension treated within a single effective framework.
- Low-density saturation: deviations arise from a bounded geometric response in diffuse environments.
- No halo-by-halo tuning: a single universal scale governs all systems.
- Void sensitivity: cosmic voids identified as maximal probes of the saturated regime.
- Falsifiability: clear observational signatures allowing confirmation or exclusion.
Ultra-diffuse galaxies
Ultra-diffuse galaxies provide extreme tests of the framework. In this regime, large apparent mass discrepancies arise as geometric threshold effects rather than from extended distributions of unseen matter.
This leads to falsifiable predictions. Independent mass tracers such as weak lensing or satellite dynamics should not reveal massive extended halos in the deepest saturation regime. A positive detection would directly falsify the model.
Relation to the Cosmochrony program
This article focuses exclusively on late-time observational consequences. The broader theoretical motivations for bounded-response regimes are developed in companion works, but are not required to follow or evaluate the present phenomenological analysis.
References
Jérôme Beau. A Unified Effective Mechanism for Galaxy Rotation Curves and the Hubble Tension. Preprint, Zenodo. 10.5281/zenodo.18452299