On the numerology of ramification data for power series in characteristic p

Abstract

Let k be a perfect field of characteristic p and set K = k((t)). In this paper we study the ramification properties of elements of Aut k (K). By choosing a uniformizer for K we may interpret our theorems in terms of power series over k.The most important tool that we use is the field of norms construction of Fontaine and Wintenberger.