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Definability under duality. (English) Zbl 1226.03053
Summary: It is shown that if \(A\) is an analytic class of separable Banach spaces with separable dual, then the set \(A^*=\{Y : \exists X\in A\) with \(Y\cong X^*\}\) is analytic. The corresponding result for pre-duals is false.

MSC:
03E15 Descriptive set theory
46B10 Duality and reflexivity in normed linear and Banach spaces
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