English

Good rings and homogeneous polynomials

Commutative Algebra 2020-10-13 v3 Algebraic Geometry

Abstract

In 2011, Khurana, Lam and Wang define the following property. (*)A commutative unital ring A satisfies the property ''power stable range one'' if for all a, b \in A with aA + bA = A there are an integer N = N (a, b) \ge 1 and λ\lambda = λ\lambda(a, b) \in A such that b N + λ\lambdaa \in A x , the unit group of A. In 2019, Berman and Erman consider rings with the following property (**) A commutative unital ring A has enough homogeneous polynomials if for any k \ge 1 and set S := {p 1 , p 2 , ..., p k } , of primitive points in A n and any n \ge 2, there exists an homogeneous polynomial P (X 1 , X 2 , ..., X n) \in A[X 1 , X 2 , ..., X n ]) with deg P \ge 1 and P (p i) \in A x for 1 \le i \le k. We show in this article that the two properties (*) and (**) are equivalent and we shall call a commutative unital ring with these properties a good ring. When A is a commutative unital ring of pictorsion as defined by Gabber, Lorenzini and Liu in 2015, we show that A is a good ring. Using a Dedekind domain we built by Goldman in 1963,we show that the converse is false.

Keywords

Cite

@article{arxiv.1907.05655,
  title  = {Good rings and homogeneous polynomials},
  author = {J. Fresnel and Michel Matignon},
  journal= {arXiv preprint arXiv:1907.05655},
  year   = {2020}
}

Comments

The paper is reorganized, some historical comments are added and some proofs are streamlined following referee's suggestions

R2 v1 2026-06-23T10:19:25.768Z