The problem of approximation by accretive elements in a unital C*-algebra suggested by P. R. Halmos is substantially solved. The key idea is the observation that accretive approximation can be regarded as a combination of positive and self-adjoint approximation. The approximation results are proved both in the C*-norm and in another, topologically equivalent norm.
@article{bwmeta1.element.bwnjournal-article-smv117i2p115bwm,
author = {Reiner Berntzen},
title = {Accretive approximation in C*-algebras},
journal = {Studia Mathematica},
volume = {119},
year = {1996},
pages = {115-121},
zbl = {0838.47009},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-smv117i2p115bwm}
}
Berntzen, Reiner. Accretive approximation in C*-algebras. Studia Mathematica, Tome 119 (1996) pp. 115-121. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-smv117i2p115bwm/
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