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Extremal cross-polytopes and Gaussian vectors

  • Gergely Ambrus EMAIL logo
Published/Copyright: January 14, 2015
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Abstract

For n ≥ 1, let ξ1, ..., ξn be independent, identically distributed standard normal variables. Among nonnegative real vectors u = (u1, . . . , un) of Euclidean norm 1, the quantity E∥(u1ξ1,..., unξn is maximised when u has at most two non-zero entries, and it is minimised when u is proportional to (1,...,1). Further generalisations of this result are also discussed. As a corollary, a lower bound on the mean width of a general convex body K is derived in terms of the successive inner radii of K.

Received: 2013-2-7
Revised: 2013-6-21
Published Online: 2015-1-14
Published in Print: 2015-1-1

© 2015 by Walter de Gruyter Berlin/Boston

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