Descriptive Set Theoretic Methods Applied to Strictly Singular and Strictly Cosingular Operators

Descriptive Set Theoretic Methods Applied to Strictly Singular and Strictly Cosingular Operators

The class of strictly singular operators originating from the dual of a separable Banach space is written as an increasing union of ω1 subclasses which are defined using the Schreier sets. A question of J. Diestel, of whether a similar result can be stated for strictly cosingular operators, is studied.

m at h . FA ] 3 1 M ay 2 00 8 DESCRIPTIVE SET THEORETIC METHODS APPLIED TO STRICTLY SINGULAR AND STRICTLY COSINGULAR OPERATORS

The class of strictly singular operators originating from the dual of a separable Banach space is written as an increasing union of ω1 subclasses which are defined using the Schreier sets. A question of J. Diestel, of whether a similar result can be stated for strictly cosingular operators, is studied.

Domination by Positive Disjointly Strictly Singular Operators

We prove that each positive operator from a Banach lattice E to a Banach lattice F with a disjointly strictly singular majorant is itself disjointly strictly singular provided the norm on F is order continuous. We prove as well that if S : E → E is dominated by a disjointly strictly singular operator, then S2 is disjointly strictly singular.

operators on L ( L p ) and ` p - strictly singular operators

A classification of weakly compact multiplication operators on L(Lp), 1 < p < ∞, is given. This answers a question raised by Saksman and Tylli in 1992. The classification involves the concept of `p-strictly singular operators, and we also investigate the structure of general `p-strictly singular operators on Lp . The main result is that if an operator T on Lp , 1 < p < 2, is `p-strictly singula...

Compact and strictly singular operators on certain function spaces