Vanishing of the first big Cohen–Macaulay Hilbert coefficient and BCM-rationality

Let (R,m)(R,\mathfrak{m}) be a Noetherian local ring such that its completion R^\widehat{R} is reduced and satisfies Serre's S2S_2 condition. Let BB be a balanced big Cohen–Macaulay RR-algebra satisfying the condition in the source. For a parameter ideal QRQ\subseteq R, let e1B(Q)e_1^B(Q) denote the first Hilbert coefficient associated to BB, and let RR be BCMB\operatorname{BCM}_B-rational when it is Cohen–Macaulay and the natural map Hmd(R)Hmd(B)H^d_{\mathfrak{m}}(R)\to H^d_{\mathfrak{m}}(B) is injective, where d=dimRd=\dim R. Vanishing conjecture for the first big Cohen–Macaulay Hilbert coefficient. If e1B(Q)=0e_1^B(Q)=0 for some parameter ideal QRQ\subseteq R, then RR is BCMB\operatorname{BCM}_B-rational. In particular, if RR is excellent of characteristic p>0p>0, its completion is reduced and satisfies S2S_2, and e1(Q)=0e_1^*(Q)=0 for some parameter ideal QRQ\subseteq R, then RR is FF-rational. This conjecture extends Huneke's question beyond the Cohen–Macaulay setting and to all characteristics; the stated condition on BB is referenced in the source but not defined in the supplied text, and the resolution status is not established here.

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Primary source

Linquan Ma and Pham Hung Quy, “Vanishing and non-negativity of the first normal Hilbert coefficient”, arXiv:2301.13084 (2024).

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