On the Karas type theorems for the multidegrees of polynomial automorphisms

摘要

To solve Nagata's conjecture, Shestakov-Umirbaev constructed a theory for deciding wildness of polynomial automorphisms in three variables. Recently, Karas and others studied multidegrees of polynomial automorphisms as an application of this theory. They give various necessary conditions for triples of positive integers to be multidegrees of tame automorphisms in three variables. In this paper, we prove a strong theorem unifying and generalizing these results using the generalized Shestakov-Umirbaev theory. (C) 2014 Elsevier Inc. All rights reserved.