Abstract
Let X be a Banach space. We give characterizations of when \( \mathcal{F}(Y,X) \) is a u-ideal in \( \mathcal{W}(Y,X) \) for every Banach space Y in terms of nets of finite rank operators approximating weakly compact operators. Similar characterizations are given for the cases when \( \mathcal{F}(X,Y) \) is a u-ideal in \( \mathcal{W}(X,Y) \) for every Banach space Y, when \( \mathcal{F}(Y,X) \) is a u-ideal in \( \mathcal{W}(Y,X^{ * * } ) \) for every Banach space Y, and when \( \mathcal{F}(Y,X) \) is a u-ideal in \( \mathcal{K}(Y,X^{ * * } ) \) for every Banach space Y.
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Abrahamsen, T.A., Lima, Å. & Lima, V. Unconditional ideals of finite rank operators. Czech Math J 58, 1257–1278 (2008). https://doi.org/10.1007/s10587-008-0085-9
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DOI: https://doi.org/10.1007/s10587-008-0085-9