## Proceedings of the American Mathematical Society
/ v.127 no.5. 1999, pp.1337-1338

Author :

Abstract :
Suppose that a and b are elements of a complex unital Banach algebra such that the spectra of a and b are 2 $\pi $ i-congruence-free. E.M.E. Wermuth has shown that then e $^{a}$ e $^{b}$ = elt;LA e $^{b}$ e $^{a}$ implies that ab = ba. In this note we use two elementary facts concerning inner derivations on Banach algebras to give a very short proof of Wermuths result.

Keyword :
Primary 46H99 . Commuting exponentials

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