On (a, B, c)-ideals in Banach spaces
Author(s) -
Ksenia Niglas,
Indrek Zolk
Publication year - 2014
Publication title -
acta et commentationes universitatis tartuensis de mathematica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.276
H-Index - 6
eISSN - 2228-4699
pISSN - 1406-2283
DOI - 10.12697/acutm.2014.18.11
Subject(s) - ideal (ethics) , mathematics , linear subspace , banach space , subspace topology , pure mathematics , transitive relation , type (biology) , discrete mathematics , combinatorics , mathematical analysis , ecology , philosophy , epistemology , biology
In this paper we focus on subspaces of Banach spaces that are ( a , B , c )-ideals. We study ( a , B , c )-ideals in l 2 ∞ and present easily verifiable conditions for a subspace of l 2 ∞ to be an ( a , B , c )-ideal. Our main results concern the transitivity of ( a , B , c )-ideals. We show that if X is an ( a , B , c )-ideal in Y and Y is a ( d , E , f )-ideal in Z , then X is a certain type of ideal in Z . Relying on this result, we show that if X is an ( a , B , c )-ideal in its bidual, then X is a certain type of ideal in X (2 n ) for every n ∈ N.
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