In this short note we give a short and elementary proof of a characterization of those extreme points of the closed unit ball in C*-algebras which are unitary. The result was originally proved by G. K. Pedersen using some methods from the theory of approximation by invertible elements.
@article{bwmeta1.element.bwnjournal-article-cmv74i1p99bwm,
author = {Rainer Berntzen},
title = {Extreme points of the closed unit ball in C*-algebras},
journal = {Colloquium Mathematicae},
volume = {72},
year = {1997},
pages = {99-100},
zbl = {0896.46038},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-cmv74i1p99bwm}
}
Berntzen, Rainer. Extreme points of the closed unit ball in C*-algebras. Colloquium Mathematicae, Tome 72 (1997) pp. 99-100. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-cmv74i1p99bwm/
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