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A hyperspace of convex bodies arising from tensor norms

Geometric Topology 2022-05-06 v1 Functional Analysis

Abstract

In a preceding work it is determined when a centrally symmetric convex body in Rd,\mathbb{R}^d, d=d1dl,d=d_1\cdots d_l, is the closed unit ball of a reasonable crossnorm on Rd1Rdl.\mathbb{R}^{d_1}\otimes\cdots\otimes\mathbb{R}^{d_l}. Consequently, the class of tensorial bodies is introduced, an associated tensorial Banach-Mazur distance is defined and the corresponding Banach-Mazur type compactum is proved to exist. In this paper, we introduce the hyperspace of these convex bodies. We called "the space of tensorial bodies". It is proved that the group of linear isomorphisms on Rd1Rdl\mathbb{R}^{d_1}\otimes\cdots\otimes\mathbb{R}^{d_l} preserving decomposable vectors acts properly (in the sense of Palais) on it. A convenient compact global slice for the space is constructed. With it, topological representatives for the space of tensorial bodies and the Banach-Mazur type compactum are given. Among others, it is showed that the set of ellipsoids in the class of tensorial bodies is homeomorphic to the Euclidean space of dimension p=d1(d1+1)2++dl(dl+1)2.p=\frac{d_1(d_1+1)}{2}+\cdots+\frac{d_l(d_l+1)}{2}. We also prove that both the projective and the injective tensor products of 00-symmetric convex bodies are continuous functions with respect to the Hausdorff distance.

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Cite

@article{arxiv.1910.11361,
  title  = {A hyperspace of convex bodies arising from tensor norms},
  author = {Luisa F. Higueras-Montaño},
  journal= {arXiv preprint arXiv:1910.11361},
  year   = {2022}
}

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23 pages