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

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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 Q⊆RQ\subseteq R, let e1B(Q)e_1^B(Q) denote the first Hilbert coefficient associated to BB, and let RR be BCM⁡B\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=dim⁡Rd=\dim R. Vanishing conjecture for the first big Cohen–Macaulay Hilbert coefficient. If e1B(Q)=0e_1^B(Q)=0 for some parameter ideal Q⊆RQ\subseteq R, then RR is BCM⁡B\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 Q⊆RQ\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.

References

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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