English

Multidegrees of Tame automorphisms with one prime number

Commutative Algebra 2012-04-10 v2

Abstract

Let 3d1d2d33\leq d_1\leq d_2\leq d_3 be integers. We show the following results: (1) If d2d_2 is a prime number and d1gcd(d1,d3)2\frac{d_1}{\gcd(d_1,d_3)}\neq2, then (d1,d2,d3)(d_1,d_2,d_3) is a multidegree of a tame automorphism if and only if d1=d2d_1=d_2 or d3d1N+d2Nd_3\in d_1\mathbb{N}+d_2\mathbb{N}; (2) If d3d_3 is a prime number and gcd(d1,d2)=1\gcd(d_1,d_2)=1, then (d1,d2,d3)(d_1,d_2,d_3) is a multidegree of a tame automorphism if and only if d3d1N+d2Nd_3\in d_1\mathbb{N}+d_2\mathbb{N}. We also relate this investigation with a conjecture of Drensky and Yu, which concerns with the lower bound of the degree of the Poisson bracket of two polynomials, and we give a counter-example to this conjecture.

Keywords

Cite

@article{arxiv.1204.0930,
  title  = {Multidegrees of Tame automorphisms with one prime number},
  author = {Jiantao Li and Xiankun Du},
  journal= {arXiv preprint arXiv:1204.0930},
  year   = {2012}
}