Definable non-divisible Henselian valuations

Abstract

On a Henselian valued field (K, V), where V is the valuation ring, if the value group contains a convex p-regular subgroup that is not p-divisible, then V is definable in the language of rings. A Henselian valuation ring with a regular non-divisible value group is always 0-definable. In particular, some results of Ax and of Konenigmann are generalized.