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Sharp One-Dimensional Sub-Gaussian Comparison in Convex Order

Probability 2026-04-30 v1 Information Theory math.IT Statistics Theory Machine Learning Statistics Theory

Abstract

We prove that any random variable XX whose moment generating function is point-wise upper bounded by that of GN(0,1) G \sim \mathcal{N}(0,1) must be dominated by G/E[G] G/\mathbb{E}[|G|] in convex order, meaning E[f(X)]E[f(G/E[G])] \mathbb{E}[f(X)] \le \mathbb{E}[f(G/\mathbb{E}[|G|])] for all convex ff. Equality is attained by taking XUnif({1,1}) X \sim \mathrm{Unif}(\{-1,1\}) and f(x)=x f(x) = |x| .

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Cite

@article{arxiv.2604.26819,
  title  = {Sharp One-Dimensional Sub-Gaussian Comparison in Convex Order},
  author = {Yihan Zhang},
  journal= {arXiv preprint arXiv:2604.26819},
  year   = {2026}
}
R2 v1 2026-07-01T12:41:42.146Z