Subspaces of the nonstandard hull of a normed space

Henson, C. Ward; Moore, L. C.

doi:10.1090/S0002-9947-1974-0365098-7

Subspaces of the nonstandard hull of a normed space
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by C. Ward Henson and L. C. Moore

Trans. Amer. Math. Soc. 197 (1974), 131-143

DOI: https://doi.org/10.1090/S0002-9947-1974-0365098-7

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Abstract:

Normed spaces which are isomorphic to subspaces of the nonstandard hull of a given normed space are characterized. As a consequence it is shown that a normed space is B-convex if and only if the nonstandard hull contains no subspace isomorphic to ${l_1}$ and a Banach space is super-reflexive if and only if the nonstandard hull is reflexive. Also, embeddings of second dual spaces into the nonstandard hull are studied. In particular, it is shown that the second dual space of a normed space E is isometric to a complemented subspace of the nonstandard hull of E.

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Nonstandard analysis

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