Quasi-Jordan Banach Algebras

We initiate a study of quasi-Jordan normed algebras. It is demonstrated that any quasi-Jordan Banach algebra with a norm 1 unit can be given an equivalent norm making the algebra isometrically isomorphic to a closed right ideal of a unital split quasi-Jordan Banach algebra; the set of invertible ele...

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Main Authors: Reem K. Alhefthi, Akhlaq A. Siddiqui, Fatmah B. Jamjoom
Format: Article
Language:English
Published: Wiley 2014-01-01
Series:Abstract and Applied Analysis
Online Access:http://dx.doi.org/10.1155/2014/690806
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author Reem K. Alhefthi
Akhlaq A. Siddiqui
Fatmah B. Jamjoom
author_facet Reem K. Alhefthi
Akhlaq A. Siddiqui
Fatmah B. Jamjoom
author_sort Reem K. Alhefthi
collection DOAJ
description We initiate a study of quasi-Jordan normed algebras. It is demonstrated that any quasi-Jordan Banach algebra with a norm 1 unit can be given an equivalent norm making the algebra isometrically isomorphic to a closed right ideal of a unital split quasi-Jordan Banach algebra; the set of invertible elements may not be open; the spectrum of any element is nonempty, but it may be neither bounded nor closed and hence not compact. Some characterizations of the unbounded spectrum of an element in a split quasi-Jordan Banach algebra with certain examples are given in the end.
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spelling doaj-art-dec9513f15a1479a93df75345f1e17e12025-02-03T05:58:51ZengWileyAbstract and Applied Analysis1085-33751687-04092014-01-01201410.1155/2014/690806690806Quasi-Jordan Banach AlgebrasReem K. Alhefthi0Akhlaq A. Siddiqui1Fatmah B. Jamjoom2Department of Mathematics, College of Science, King Saud University, P.O. Box 2455-5, Riyadh 11451, Saudi ArabiaDepartment of Mathematics, College of Science, King Saud University, P.O. Box 2455-5, Riyadh 11451, Saudi ArabiaDepartment of Mathematics, College of Science, King Saud University, P.O. Box 2455-5, Riyadh 11451, Saudi ArabiaWe initiate a study of quasi-Jordan normed algebras. It is demonstrated that any quasi-Jordan Banach algebra with a norm 1 unit can be given an equivalent norm making the algebra isometrically isomorphic to a closed right ideal of a unital split quasi-Jordan Banach algebra; the set of invertible elements may not be open; the spectrum of any element is nonempty, but it may be neither bounded nor closed and hence not compact. Some characterizations of the unbounded spectrum of an element in a split quasi-Jordan Banach algebra with certain examples are given in the end.http://dx.doi.org/10.1155/2014/690806
spellingShingle Reem K. Alhefthi
Akhlaq A. Siddiqui
Fatmah B. Jamjoom
Quasi-Jordan Banach Algebras
Abstract and Applied Analysis
title Quasi-Jordan Banach Algebras
title_full Quasi-Jordan Banach Algebras
title_fullStr Quasi-Jordan Banach Algebras
title_full_unstemmed Quasi-Jordan Banach Algebras
title_short Quasi-Jordan Banach Algebras
title_sort quasi jordan banach algebras
url http://dx.doi.org/10.1155/2014/690806
work_keys_str_mv AT reemkalhefthi quasijordanbanachalgebras
AT akhlaqasiddiqui quasijordanbanachalgebras
AT fatmahbjamjoom quasijordanbanachalgebras