Hirsch and van der Marel's 2022 technical analysis concludes CSH's reported susceptibility data are a smoothly-varying spline plus a quantized artifact, not a genuine background subtraction

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Dirk van der Marel and Jorge Hirsch's joint "Extended Comment" (arXiv:2201.07686, later published in International Journal of Modern Physics B) analyzes the raw data Ranga Dias and Ashkan Salamat eventually posted for the retracted carbonaceous-sulfur-hydride (CSH) paper. Across all six reported pressures, they conclude the background-corrected susceptibility data are "pathological," were not produced by either the method the original paper described or any of three alternative methods the authors later supplied, and that the data labeled "measured voltage" are not raw measurements at all.

The specific technical finding underlying that verdict: the reported "superconducting signal" decomposes into a smoothly-varying spline component plus a quantized (discretized) component — a combination that should not be able to survive an honest subtraction of two independently noisy measurements, since real subtraction of two noisy signals does not produce clean discretization artifacts. Van der Marel and Hirsch also report that the correlations between the reported "raw" and "corrected" data run in the direction predicted if a background curve was added to a smooth, pre-existing target curve, rather than subtracted from an independently measured raw signal — the reverse of what the paper's stated method describes.

This is the specific statistical mechanism behind the more general claim in claim-hirsch-forensics-drove-dias-superconductivity-retraction that the CSH data were "too smooth" to be genuine; it converges with Nature's own retraction rationale (see claim-nature-2022-csh-retraction-cites-undisclosed-background-subtraction) and follows the precedent-modeling described in claim-hirsch-modeled-csh-critique-on-2009-debessai-europium-precedent.