English

The Hilbert Schmidt version of the commutator theorem for zero trace matrices

Functional Analysis 2017-05-17 v1

Abstract

Let AA be a m×mm\times m complex matrix with zero trace. Then there are m×mm\times m matrices BB and CC such that A=[B,C]A=[B,C] and BC2(logm+O(1))1/2A2\|B\|\|C\|_2\le (\log m+O(1))^{1/2}\|A\|_2 where D\|D\| is the norm of DD as an operator on 2m\ell_2^m and D2\|D\|_2 is the Hilbert--Schmidt norm of DD. Moreover, the matrix BB can be taken to be normal. Conversely there is a zero trace m×mm\times m matrix AA such that whenever A=[B,C]A=[B,C], BC2logmO(1)1/2A2\|B\|\|C\|_2\ge |\log m-O(1)|^{1/2}\|A\|_2 for some absolute constant c>0c>0.

Keywords

Cite

@article{arxiv.1503.07980,
  title  = {The Hilbert Schmidt version of the commutator theorem for zero trace matrices},
  author = {Omer Angel and Gideon Schechtman},
  journal= {arXiv preprint arXiv:1503.07980},
  year   = {2017}
}
R2 v1 2026-06-22T09:03:30.382Z