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Smooth flat maps over commutative DG-rings

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Abstract

We study smooth maps that arise in derived algebraic geometry. Given a map \(A \rightarrow B\) between non-positive commutative noetherian DG-rings which is of flat dimension 0, we show that it is smooth in the sense of Toën–Vezzosi if and only if it is homologically smooth in the sense of Kontsevich. We then show that B, being a perfect DG-module over \(B\otimes ^{{\mathrm {L}}}_A B\) has, locally, an explicit semi-free resolution as a Koszul complex. As an application we show that a strong form of Van den Bergh duality between (derived) Hochschild homology and cohomology holds in this setting.

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Notes

  1. Here, by flat we mean a map of flat dimension 0. See Sect. 1.2 for the precise definition.

  2. To be precise, we show that the fact that a specific map being a quasi-isomorphism is equivalent to the other conditions. See Corollary 3.7.

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Acknowledgements

The author thanks Amnon Yekutieli for helpful discussions. The author is thankful to an anonymous referee for several corrections that helped significantly improving this manuscript. This work has been supported by the Charles University Research Centre program No.UNCE/SCI/022, and by the Grant GA ČR 20-02760Y from the Czech Science Foundation.

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Correspondence to Liran Shaul.

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Shaul, L. Smooth flat maps over commutative DG-rings. Math. Z. 299, 1673–1688 (2021). https://doi.org/10.1007/s00209-021-02748-0

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