A conductor formula for completed group algebras

Abstract

Let $\mathcal O$ be the ring of integers in a finite extension of $\mathbb Q_p$. If $G$ is a finite group and $\Gamma$ is a maximal order containing the group ring $\mathcal O[G]$, Jacobinski's conductor formula gives a complete description of the central conductor of $\Gamma$ into $\mathcal O[G]$ in terms of characters of $G$. We prove a similar result for completed group algebras $\mathcal O[[G]]$, where $G$ is a $p$-adic Lie group of dimension $1$. We will also discuss several consequences of this result.