The Paulsen Problem Made Simple

09/13/2018

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by   Linus Hamilton, et al.

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The Paulsen problem is a basic problem in operator theory that was resolved in a recent tour-de-force work of Kwok, Lau, Lee and Ramachandran. In particular, they showed that every ϵ-nearly equal norm Parseval frame in d dimensions is within squared distance O(ϵ d^13/2) of an equal norm Parseval frame. We give a dramatically simpler proof based on the notion of radial isotropic position, and along the way show an improved bound of O(ϵ d^2).