Abstract
It is proved using positive definite functions that a normed spaceX is unifomly homeomorphic to a subset of a Hilbert space, if and only ifX is (linearly) isomorphic to a subspace of aL 0(μ) space (=the space of the measurable functions on a probability space with convergence in probability). As a result we get thatl p (respectivelyL p (0, 1)), 2<p<∞, is not uniformly embedded in a bounded subset of itself. This answers negatively the question whether every infinite dimensional Banach space is uniformly homeomorphic to a bounded subset of itself. Positive definite functions are also used to characterize geometrical properties of Banach spaces.
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Partially supported by the National Science Foundation, Grant MCS-79-03322.
Partially supported by the National Science Foundation, Grant MCS-80-06073.
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Aharoni, I., Maurey, B. & Mityagin, B.S. Uniform embeddings of metric spaces and of banach spaces into hilbert spaces. Israel J. Math. 52, 251–265 (1985). https://doi.org/10.1007/BF02786521
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DOI: https://doi.org/10.1007/BF02786521