English

Note on Wermuth's theorem on commuting operator exponentials

Functional Analysis 2025-04-09 v2 Operator Algebras Rings and Algebras

Abstract

We apply Wermuth's theorem on commuting operator exponentials to show that if A,BB(X)A, B \in B(X), XX being Banach space and AA of 2πi2\pi i-congruence free spectrum, then eAB=BeAe^A B = B e^A if and only if AB=BAAB=BA. We employ this observation to provide alternative proof of similar result by Chaban and Mortad, applicable for XX being a Hilbert space.

Keywords

Cite

@article{arxiv.1901.10261,
  title  = {Note on Wermuth's theorem on commuting operator exponentials},
  author = {Krzysztof Szczygielski},
  journal= {arXiv preprint arXiv:1901.10261},
  year   = {2025}
}

Comments

4 pages, no figures. Results largely incorporated into arXiv:2504.01176

R2 v1 2026-06-23T07:25:31.045Z