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On a result of J. Johnson. (English) Zbl 0869.46011

The space \({\mathcal K}(E,F)\) of compact operators is, in general, not complemented in the space \({\mathcal L}(E,F)\) of all continuous operators (\(E\), \(F\) Banach spaces). The author shows, however, that the dual \({\mathcal K}(E,F)'\) is isomorphic to a complemented subspace of \({\mathcal L}(E,F)'\) (the complement being the annihilator of \({\mathcal K}(E,F)\)) – provided that every operator \(T:E\to F\) factors through a Banach space \(Z_T\) with the bounded approximation property and separable dual. For \(F'\) being separable this generalizes a former result of J. Johnson \(Z_T= F\) for all \(T\) in [J. Funct. Anal. 32, 304-311 (1979; Zbl 0412.47024)] and for \(E=P\) and \(F=P'\) (where \(P\) is any separable Pisier space hence \(Z_T=\ell_2\)) this is also due to K. John [Note Mat. 12, 69-75 (1992; Zbl 0802.46015)].

MSC:

46B28 Spaces of operators; tensor products; approximation properties

References:

[1] G.Godefroy, P. Saphar:: Duality in spaces of operators and smooth norms on Banach spaces. Illinois Journal Math. 32 No. 4 (1988), 672-695. · Zbl 0631.46015
[2] G. Godefroy, N.J. Kalton, P.D. Saphar: Unconditional ideals in Banach spaces. Studia Math. 104 (1993), 13-59. · Zbl 0814.46012
[3] K. John: On the space \(K(P,P^*)\) of compact operators on Pisier space \(P\). Note di Matematica 12 (1992), 69-75. · Zbl 0802.46015
[4] J. Johnson: Remarks on Banach spaces of compact operators. Funct. Anal. 32 (1979), 304-311. · Zbl 0412.47024 · doi:10.1016/0022-1236(79)90042-9
[5] W.B. Johnson, H.P. Rosenthal, M. Zippin: On bases, finite dimensional decompositions and weaker structures in Banach spaces. Israel J. M. 9 (1971), 488-506. · Zbl 0217.16103 · doi:10.1007/BF02771464
[6] N.J. Kalton: Spaces of compact operators. Math. Ann. 208 (1974), 267-278. · Zbl 0266.47038 · doi:10.1007/BF01432152
[7] A. Pietsch: Operator Ideals. Deutscher Verlag der Wissenschaften, Berlin, 1978. · Zbl 0405.47027
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