Perfectoid purity under flat local base change

Let (R,m)(R,\mathfrak{m}) be a Noetherian local ring and let (R,m)(S,n)(R,\mathfrak{m})\subseteq(S,\mathfrak{n}) be a flat local homomorphism. The flat base-change conjecture. If RR is perfectoid pure and S/mSS/\mathfrak{m}S is regular (or even Gorenstein FF-pure), then SS is perfectoid pure; and if RR is perfectoid injective and S/mSS/\mathfrak{m}S is Cohen–Macaulay and geometrically FF-injective, then SS is perfectoid injective. This is expected in view of the positive-characteristic theory, but the authors do not know how to prove it.

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Primary source

Bhargav Bhatt, Linquan Ma, Zsolt Patakfalvi, Karl Schwede, Kevin Tucker, Joe Waldron and Jakub Witaszek, “Perfectoid pure singularities”, arXiv:2409.17965 (2026).

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