The p-adic Kummer-Leopoldt constant - Normalized p-adic regulator

Abstract

The p-adic Kummer--Leopoldt constant kappa\_K of a number field K is (assuming the Leopoldt conjecture) the least integer c such that for all n \textgreater{}\textgreater{} 0, any global unit of K, which is locally a p^(n+c)th power at the p-places, is necessarily the p^nth power of a global unit of K. This constant has been computed by Assim \& Nguyen Quang Do using Iwasawa's techniques,after intricate studies and calculations by many authors. We give an elementary p-adic proof and an improvement of these results, then a class field theory interpretation of kappa\_K. We give some applications (including generalizations of Kummer's lemma on regular pth cyclotomic fields) and a natural definition of the normalized p-adic regulator for any K and any p$\ge$2.This is done without analytical computations, using only class field theoryand especially the properties of the so-called p-torsion group T\_K of Abelian p-ramification theory over K.

To appear in "International Journal of Number Theory" (2018)

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