English

Products of commutators in simple algebras

Rings and Algebras 2025-09-30 v1

Abstract

Let AA be a finite-dimensional simple algebra that is not a field. We show that every aAa\in A can be written as a=(bccb)(deed)a=(bc-cb)(de-ed) for some b,c,d,eAb,c,d,e\in A. This is not always true for infinite-dimensional simple algebras. In fact, for any mNm\in \mathbb N we provide an example of an infinite-dimensional simple unital CC^*-algebra AA in which 11 cannot be written as i=1mxi(aibibiai)yi\sum_{i=1}^m x_i(a_ib_i-b_ia_i)y_i for some xi,ai,bi,yiAx_i,a_i,b_i,y_i\in A.

Keywords

Cite

@article{arxiv.2509.23956,
  title  = {Products of commutators in simple algebras},
  author = {Matej Brešar and Hau-Yuan Jang and Leonel Robert},
  journal= {arXiv preprint arXiv:2509.23956},
  year   = {2025}
}