Relative affinization conjecture for the filtered nodal curve

From papers

Let RR be a commutative ring, and let

[A1/Gm]Mcub[\mathbb{A}^1/\mathbb{G}_{m}]\to \mathcal{M}_{cub}

be the map classifying the filtered nodal curve over RR. Denote the corresponding filtered nodal curve by Nfil\mathcal{N}_{\mathrm{fil}}, and let Sfil1S^1_{\mathrm{fil}} be the filtered circle of Moulinos, Robalo, and Toën. Relative affinization conjecture. The relative affinization of Nfil\mathcal{N}_{\mathrm{fil}} is equivalent to the filtered circle:

Aff[A1/Gm](Nfil)Sfil1.\operatorname{Aff}_{[\mathbb{A}^1/\mathbb{G}_{m}]}(\mathcal{N}_{\mathrm{fil}})\simeq S^1_{\mathrm{fil}}.

Consequently, for every affine scheme XX over RR, there is an equivalence

HHfil(X)O ⁣(Map[A1/Gm](Aff[A1/Gm](Nfil),X×[A1/Gm])).\mathrm{HH}_*^{\mathrm{fil}}(X)\simeq \mathcal{O}\!\left(\operatorname{Map}_{[\mathbb{A}^1/\mathbb{G}_{m}]}\left(\operatorname{Aff}_{[\mathbb{A}^1/\mathbb{G}_{m}]}(\mathcal{N}_{\mathrm{fil}}),X\times[\mathbb{A}^1/\mathbb{G}_{m}]\right)\right).

This would explain the parallelism between tmf-Hochschild homology and filtered Hochschild homology through the degeneration from the nodal cubic to the cuspidal cubic. The source presents the assertion as a conjectural description.

Progress summary

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Sources & referencesView supporting material

Primary source

Sarah Scherotzke, Nicolò Sibilla and Paolo Tomasini, “Fourier–Mukai equivalences for formal groups and elliptic Hochschild homology”, arXiv:2505.00172 (2025).

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