Parameterizing Conjugacy Classes of Unramified Tori via Bruhat-Tits Theory

Abstract

Suppose $k$ is a nonarchimedean local field, $K$ is a maximally unramified extension of $k$, and $\mathbf{G}$ is a connected reductive $k$-group. In this paper we provide parameterizations via Bruhat-Tits theory of: the rational conjugacy classes of $k$-tori in $\mathbf{G}$ that split over $K$; the rational and stable conjugacy classes of the $K$-split components of the centers of unramified twisted Levi subgroups of $\mathbf{G}$; and the rational conjugacy classes of unramified twisted generalized Levi subgroups of $\mathbf{G}$. We also provide parameterizations of analogous objects for finite groups of Lie type.