Hochster's small Cohen–Macaulay conjecture

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Let (R,m)(R,\mathfrak{m}) be a complete local ring. A small Cohen–Macaulay module over RR is a nonzero finitely generated RR-module SS such that depth⁡(S)=dim⁡(R)\operatorname{depth}(S)=\dim(R). Hochster's small Cohen–Macaulay conjecture. Every complete local ring admits a small Cohen–Macaulay module. The conjecture asks whether finite Cohen–Macaulay modules exist for all complete local rings; the paper's abstract indicates that, in mixed characteristic and dimension at least four, there are normal local domains with no small Cohen–Macaulay algebra, while still admitting small Cohen–Macaulay modules.

References

Primary source

Kazuma Shimomoto and Ehsan Tavanfar, “On local rings without small Cohen-Macaulay algebras in mixed characteristic”, arXiv:2109.12700 (2024).

Additional references

4 papers in this index state this conjecture (2010–2021). The statement above is taken from the most recent of them; the others are arXiv:1310.0389, arXiv:1203.0907, arXiv:1005.3275.

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