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Abstract. In this note we first make a modest improvement of an inequality of Brown--Lomonosov--Simonic on certain transitive operator algebras. Then we use a result of Foias--Pasnicu--Voiculescu to provide similar inequalities for algebras generated by a quasitriangular operator.
AMS Subject Classification
(1991): 47A15
Keyword(s):
Invariant subspace,
hyperinvariant subspace,
quasitriangular,
transitive operator
Received January 3, 2008, and in revised form February 11, 2008. (Registered under 6014/2009.)
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