Crystalline condition for $A_{\mathrm{inf}}$-cohomology and ramification bounds

TL;DR

This paper introduces a series of conditions ($\mathrm{Cr}_s$) on prismatic cohomology that control Galois actions, leading to new criteria for crystallinity and ramification bounds in p-adic geometry.

Contribution

It develops new conditions ($\mathrm{Cr}_s$) on prismatic cohomology to analyze Galois actions, providing criteria for crystallinity and improved ramification bounds in p-adic cohomology.

Findings

Criterion ($\mathrm{Cr}_0$) for crystallinity of Galois representations.

Extension of ramification bounds to arbitrary $e$ and $i$.

Avoids crystalline comparison in proving crystallinity.

Abstract

For a prime $p>2$ and a smooth proper $p$-adic formal scheme $X$ over $\mathcal{O}_K$ where $K$ is a $p$-adic field, we study a series of conditions ($\mathrm{Cr}_s$), $s\geq 0$ that partially control the $G_K$-action on the image of the associated Breuil-Kisin prismatic cohomology $\mathrm{R}\Gamma_{\Delta}(X/\mathfrak{S})$ inside the $A_{\mathrm{inf}}$-prismatic cohomology $\mathrm{R}\Gamma_{\Delta}(X_{A_{\mathrm{inf}}}/A_{\mathrm{inf}})$. The condition ($\mathrm{Cr}_0$) is a criterion for a Breuil-Kisin-Fargues $G_K$-module to induce a crystalline representation used by Gee and Liu, and thus leads to a proof of crystallinity of $\mathrm{H}^i_{\text{\'{e}t}}(X_{\overline{\eta}}, \mathbb{Q}_p)$ that avoids the crystalline comparison. The higher conditions ($\mathrm{Cr}_s$) are used to adapt the strategy of Caruso and Liu in order to establish ramification bounds for the mod $p$ representations $\mathrm{H}^{i}_{\text{\'{e}t}}(X_{\overline{\eta}}, \mathbb{Z}/p\mathbb{Z}),$ for arbitrary $e$ and $i$, which extend or improve existing bounds in various situations.