Abelian-by-Central Galois Groups of Fields II: Definability of Inertia/Decomposition Groups

Abstract

This paper explores some first-order properties of commuting-liftable pairs in pro-$\ell$ abelian-by-central Galois groups of fields. The main focus of the paper is to prove that minimized inertia and decomposition groups of many valuations are first-order definable using a predicate for the collection of commuting-liftable pairs.

V2: 24 pages; minor changes/corrections