We present Stage Σ of the Criterion C2 relativistic consistency program: a rigid, fixed–baseline closure diagnostic of the Weyl (gravitational lensing) sector using real Dark Energy Survey Year 3 (DES Y3) MagLim weak–lensing two–point statistics. All background cosmological parameters and DES nuisance parameters are held fixed to the official DES Y3 baseline best–fit values. The Weyl sector is then probed through a single global amplitude deformation Σ applied to a baseline theory vector in the known DES Y3 MagLim data–vector ordering (with the appropriate powers for each two–point type). Over broad scale ranges, this intentionally restrictive one–parameter closure hypothesis provides a statistically unacceptable description of the data. We interpret this outcome as evidence that the rigid, frozen–baseline closure ansatz is insufficient for the DES Y3 lensing two–point products under the present construction (e.g. residual scale/tomography structure not captured by a single amplitude), rather than as evidence for modified gravity. Accordingly, the main deliverable is a fully reproducible, audit–ready closure framework and a clear diagnostic baseline for subsequent iterations (controlled scale cuts, alternative validated template extraction, and systematic–stress tests) required before any cross–sector C2 statement becomes physically meaningful.
Fernando Cesar Coelho Coutinho (Wed,) studied this question.