A $p$-adic Riemann--Hilbert correspondence over Robba rings

Abstract

We construct overconvergent period sheaves $\mathcal{O}\widetilde{\mathbb{C}}^{I,\dagger}$ and $\mathcal{O}\mathbb{B}_{\mathrm{dR}}^{\dagger,+}$ on the $v$-site of a liftable semi-stable formal scheme $\mathfrak{X}_Z$. By establishing a decompletion theorem for small representations, we prove a $p$-adic Riemann-Hilbert correspondence relating small $\widetilde{\mathbb{C}}^I$-local systems (resp. $\mathbb{B}_{\mathrm{dR}}^+$-local systems) on the generic fiber $X_Z$ to small flat connections on the associated period ringed spaces. We further analyze the local Frobenius action and show that this correspondence is compatible with the Frobenius structure. As an application, we prove a comparison theorem between the cohomology of these period sheaves and the rigid cohomology of the special fiber, refining results of Le Bras and Colmez--Nizioł.