English

The Nagata automorphism is shifted linearizable

Algebraic Geometry 2008-05-01 v1 Commutative Algebra Complex Variables

Abstract

A polynomial automorphism FF is called {\em shifted linearizable} if there exists a linear map LL such that LFLF is linearizable. We prove that the Nagata automorphism N:=(XYΔZΔ2,Y+ZΔ,Z)N:=(X-Y\Delta -Z\Delta^2,Y+Z\Delta, Z) where Δ=XZ+Y2\Delta=XZ+Y^2 is shifted linearizable. More precisely, defining L(a,b,c)L_{(a,b,c)} as the diagonal linear map having a,b,ca,b,c on its diagonal, we prove that if ac=b2ac=b^2, then L(a,b,c)NL_{(a,b,c)}N is linearizable if and only if bc1bc\not = 1. We do this as part of a significantly larger theory: for example, any exponent of a homogeneous locally finite derivation is shifted linearizable. We pose the conjecture that the group generated by the linearizable automorphisms may generate the group of automorphisms, and explain why this is a natural question.

Keywords

Cite

@article{arxiv.0804.4870,
  title  = {The Nagata automorphism is shifted linearizable},
  author = {Stefan Maubach and Pierre-Marie Poloni},
  journal= {arXiv preprint arXiv:0804.4870},
  year   = {2008}
}

Comments

14 pages

R2 v1 2026-06-21T10:36:14.268Z