Semistable comparison conjecture for torsion in p-adic étale cohomology

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Let X\mathfrak{X} be a semistable formal scheme over OC\mathcal{O}_C, meaning that it has étale-locally semistable coordinates, and equip it with its canonical log structure. Let k0k^0 denote kk with the log structure associated with Z≥0→k\mathbb{Z}_{\ge 0}\to k, sending 11 to 00 and 00 to 11. Suppose that X\mathfrak{X} admits an open affine covering {Ur}r∈Z≥0\{\mathfrak{U}_r\}_{r\in \mathbb{Z}_{\ge 0}} with Ur⊆Ur+1\mathfrak{U}_r\subseteq \mathfrak{U}_{r+1}.

Semistable comparison conjecture. For all i∈Zi\in \mathbb{Z} and n∈Z≥0n\in \mathbb{Z}_{\ge 0}, there is a natural isomorphism

Hproeˊt⁡i+1(XC,Zp)[pn]≅H1(Xk/k0,WΩlog⁡i)[pn].H^{i+1}_{\operatorname{pro\acute{e}t}}(\mathfrak{X}_{C}, \mathbb{Z}_p)[p^n]\cong H^1(\mathfrak{X}_k/k^0, W\Omega_{\log}^i)[p^n].

Here WΩlog⁡iW\Omega_{\log}^i denotes logarithmic de Rham–Witt cohomology for log schemes.

This conjecture proposes extending the comparison theorem for formal schemes with smooth reduction to the semistable reduction case. The logarithmic de Rham–Witt theory used on the right-hand side is attributed to Lorenzon; the source provides no resolution status.

References

Primary source

Guido Bosco, “Torsion in p-adic étale cohomology: remarks and conjectures”, arXiv:2411.07355 (2024).

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