E12 (camels_astrid) — external validation, LCDM CV_0
Our PM evolved from CAMELS’ own 2LPT ICs (z=127→0, Ωm=0.3, 256³, 25 Mpc/h box). Node-rounding sanity: fraction of IC displacements beyond 0.45 voxels = 0.037.
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Tier 1 (truth quality): our PM vs Arepo, matched IDs: median offset 0.407 Mpc/h.
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Tier 2 (external stress test): ZA 1.140 vs damping model 1.127 Mpc/h median vs Arepo truth (0.1 Mpc cells — 10× beyond tested resolution range).
| k (h/Mpc) | r our-PM | T our-PM | r ZA | r damp |
|---|---|---|---|---|
| 0.35 | 0.999 | 0.918 | 0.982 | 0.983 |
| 0.66 | 0.984 | 0.897 | 0.924 | 0.925 |
| 1.26 | 0.937 | 0.859 | 0.702 | 0.711 |
| 2.40 | 0.838 | 0.863 | 0.144 | 0.201 |
| 4.57 | 0.574 | 0.794 | 0.017 | 0.012 |
| 8.69 | 0.293 | 0.707 | -0.001 | -0.002 |
Verdict (two-code external validation)
Same shared CV_0 ICs (per-ID prediction test: TNG-derived psi predicts Astrid’s z=15 positions to 0.068 vox median), truth from MP-Gadget instead of Arepo. Results identical to the Arepo case to three decimals (0.407 / 1.140 / 1.127 Mpc/h), explained by the decisive number: Arepo and MP-Gadget agree with each other to a median 0.029 Mpc/h per matched particle (p90 0.204). Production codes thus define a consensus truth ~14x tighter than our PM’s offset from it, and our PM’s 0.41 Mpc/h distance from that consensus is itself an order of magnitude below the 4-5 Mpc/h effects the program measures. Truth validation is closed at two independent codes.