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Abelian groups are polynomially stable

Oren Becker, Jonathan Mosheiff

Abstract

In recent years, there has been a considerable amount of interest in stability of equations and their corresponding groups. Here, we initiate the systematic study of the quantitative aspect of this theory. We develop a novel method, inspired by the Ornstein-Weiss quasi-tiling technique, to prove that abelian groups are polynomially stable with respect to permutations, under the normalized Hamming metrics on the groups $\operatorname{Sym}(n)$. In particular, this means that there exists $D\geq 1$ such that for $A,B\in \operatorname{Sym}(n)$, if $AB$ is $δ$-close to $BA$, then $A$ and $B$ are $ε$-close to a commuting pair of permutations, where $ε\leq O(δ^{1/D})$. We also observe a property-testing reformulation of this result, yielding efficient testers for certain permutation properties.

Abelian groups are polynomially stable

Abstract

In recent years, there has been a considerable amount of interest in stability of equations and their corresponding groups. Here, we initiate the systematic study of the quantitative aspect of this theory. We develop a novel method, inspired by the Ornstein-Weiss quasi-tiling technique, to prove that abelian groups are polynomially stable with respect to permutations, under the normalized Hamming metrics on the groups . In particular, this means that there exists such that for , if is -close to , then and are -close to a commuting pair of permutations, where . We also observe a property-testing reformulation of this result, yielding efficient testers for certain permutation properties.

Paper Structure

This paper contains 22 sections, 39 theorems, 161 equations.

Key Result

Proposition 1.7

AP15 Let $E_{1}$ and $E_{2}$ be equivalent equation-sets. Then $E_{1}$ is stable if and only if $E_{2}$ is stable.

Theorems & Definitions (104)

  • Example 1.1
  • Definition 1.2
  • Definition 1.3
  • Definition 1.4
  • Definition 1.5
  • Definition 1.6
  • Proposition 1.7
  • Definition 1.8
  • Theorem 1.9
  • Definition 1.10
  • ...and 94 more