The weak thin shell conjecture for log-concave random vectors

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Let XX be a log-concave random vector, let ∣⋅∣2|\cdot|_2 denote the Euclidean norm, and define its weak pp-moment by

σp(X)=sup⁡∣z∣2≤1(E∣⟨z,X⟩∣p)1/p.\sigma_p(X)=\sup_{|z|_2\le1}\left(\mathbb{E}|\langle z,X\rangle|^p\right)^{1/p}.

Weak thin shell conjecture. There exists c>0c>0 such that for every log-concave random vector XX,

∀ p≥1,(E∣X∣2p)1/p≤E∣X∣2+c σp(X).\forall\,p\ge1,\qquad \left(\mathbb{E}|X|_2^p\right)^{1/p}\le\mathbb{E}|X|_2+c\,\sigma_p(X).

This seeks to remove the multiplicative constant in the known strong-versus-weak moment estimate for log-concave vectors. It is presented as a weaker consequence suggested by the thin shell conjecture; no resolution is given.

References

Primary source

Olivier Guédon, “Concentration phenomena in high dimensional geometry”, arXiv:1310.1204 (2013).

Additional references

2 papers in this index state this conjecture (2012–2013). The statement above is taken from the most recent of them; the others are arXiv:1203.0893.

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