Lubin's conjecture for height-one $p$-adic dynamical systems over cyclo-tame extensions

TL;DR

This paper proves new cases of Lubin's conjecture by analyzing height-one $p$-adic dynamical systems over certain cyclo-tame extensions, using $p$-adic Hodge theory to connect formal groups and endomorphisms.

Contribution

It introduces a novel method to recover formal groups from commuting pairs of power series over cyclo-tame extensions, confirming Lubin's conjecture in new cases.

Findings

Extracts a crystalline character from $f$-consistent sequences.

Equips $T_f$ with a $Z_p$-module structure making $f$ an endomorphism.

Recovers a formal group over $ o_K$ for the pair $(f, u)$.

Abstract

Let $K/\mathbb{Q}_p$ be a finite extension whose ramification index is coprime to $p^2-p$. We study height-one commuting pairs $(f, u)$ of noninvertible and invertible formal power series defined over the ring of integers $\mathcal{O}_K$ of $K$. We begin by extracting a crystalline character of weight $1$ from the $\mathrm{Gal}(\overline K/K)$-set $T_f$ of $f$-consistent sequences. This character is used in order to equip $T_f$ with a $\mathbb{Z}_p$-module structure for which $f$ is an endomorphism. We then apply explicit functors in integral $p$-adic Hodge theory to $T_f$ to recover a formal group defined over $\mathcal{O}_K$ for which $(f, u)$ is a pair of endomorphisms. This proves new cases of a conjecture of Lubin.