Papers · William Alexander Aldred

The Relation Survives the Jump; the Scale Does Not: The Radial Acceleration Relation in Galaxy Clusters

Publicly deposited November 1, 2026 · Zenodo · 5 pp · DOI: 10.5281/zenodo.23864820

Abstract

On the CLASH sample's reading, galaxy clusters obey a radial acceleration relation. In that sample (Tian et al. 2020), lensing-measured total acceleration tracks X-ray baryonic acceleration along a relation parallel to the galactic RAR, with intrinsic scatter of 15% — and a characteristic scale g‡ = (2.0 ± 0.1)×10⁻⁹ m/s², which is 16.7 times the galactic scale g† = (1.20 ± 0.02)×10⁻¹⁰ m/s². The separation is 18.8σ on the fits' own errors. The cluster mass–velocity-dispersion relation repeats the pattern in a second observable: M_bar ∝ σ⁴.¹ ± ⁰.¹ over the HIFLUGCS clusters — the slope-4 form of the baryonic Tully–Fisher/Faber–Jackson family, intact, at a characteristic acceleration an order of magnitude larger. So the one-scale demand — the demand this program has been enforcing on table after table — fails at cluster scale in a specific, surgical way: the functional form of the acceleration relation is scale-free across three decades of system mass, and its constant is not. In the deep low-acceleration regime, clusters at a given baryonic acceleration pull √16.7 ≈ 4.1 times harder than the galactic scale permits; the classical statement of the same wound is the residual missing mass of roughly a factor of two that modified-dynamics analyses have always carried in cluster cores (Sanders 1999, 2003; Pointecouteau & Silk 2005), where accelerations are transitional rather than deep. Verdict: one scale does not pay beyond galaxies. A universal acceleration constant of nature is dead at cluster scale at 18.8σ. Two things this verdict is not: it is not a wound to ΛCDM, inside which a tight cluster acceleration relation is an emergent baryon–halo coupling (the CLASH authors themselves note consistency with a ΛCDM semi-analytic model), and it is not uncontested — a counter-analysis (Chan & Del Popolo 2020) disputes the cluster relation's existence, and the cluster baryon census itself runs short of the cosmic fraction, worse at low mass, which is a second defect feeding the first. All of it is printed. What this program takes home is narrower and harder than any of the camps' headlines: form, yes; constant, no. ---

The result, in plain language

Galaxy clusters, on the CLASH sample's reading, obey a radial acceleration relation — the same form as the galactic one, with 15% intrinsic scatter. But its characteristic scale is (2.0 ± 0.1)×10⁻⁹ m/s², which is 16.7 times the galactic scale. That is an 18.8σ separation on the fits' own errors, and a second observable — the cluster mass–velocity-dispersion relation, with its slope-4 form intact — repeats the pattern.

So the one-scale demand fails at cluster scale surgically: the form of the acceleration relation is scale-free across three decades of system mass, and its constant is not. In the deep regime, clusters pull about 4.1 times harder than the galactic scale permits. The verdict is printed with its boundaries: it is not a wound to ΛCDM, inside which such a relation is emergent, and it is not uncontested — the counter-analysis is printed. Form, yes; constant, no.

Program note

Cube Campaign Batch 2, target C-17 — the one-scale demand spent one system class up, on the CLASH cluster sample; every input checked against the published record during the run. Verdict, as the paper states it: one scale does not pay beyond galaxies — the radial acceleration relation's form carries to clusters but its constant does not: the cluster scale (2.0 ± 0.1)×10⁻⁹ m/s² is 16.7 times the galactic value, an 18.8σ separation on the fits' own errors. The counter-witness (Chan & Del Popolo 2020) is printed, and ΛCDM is expressly not wounded: an emergent relation has no constant to defend. The vacuum catastrophe remains unsolved, and this paper claims no result on it.

The program