Let G be the set of invertible elements of a normed algebra A with an identity. For some but not all subsets H of G we have the following dichotomy. For x ∈ A either for all c ∈ H or . In that case the set of x ∈ A for which the sup is finite is the centralizer of H.
@article{bwmeta1.element.bwnjournal-article-smv142i1p1bwm,
author = {Bertram Yood},
title = {Centralizers for subsets of normed algebras},
journal = {Studia Mathematica},
volume = {141},
year = {2000},
pages = {1-6},
zbl = {0977.46022},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-smv142i1p1bwm}
}
Yood, Bertram. Centralizers for subsets of normed algebras. Studia Mathematica, Tome 141 (2000) pp. 1-6. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-smv142i1p1bwm/
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