Abstract
We show that most of the theory of Hermitian Banach algebras can be proved for normed *-algebras without the assumption of completeness. The conditionr(x)≤p(x) for allx (wherep(x)=r(x * x) 1/2 is the Pták function), which is essential in the theory of Hermitian Banach algebras, is replaced for normed *-algebras by the conditionr(x+y)≤p(x)+p(y) for allx, y. In case of Banach *-algebras these conditions are equivalent.
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The research has been supported by a grant from La Junta de Andalucía and by the Department of Applied Mathematics, University of Seville
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Müller, V. Normed algebras with involution. Manuscripta Math 75, 197–210 (1992). https://doi.org/10.1007/BF02567080
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DOI: https://doi.org/10.1007/BF02567080