



























The Gaussian width is a fundamental quantity in probability, statistics and geometry, known to underlie the intrinsic difficulty of estimation and hypothesis testing. In this work, we show how the Gaussian width, when localized to any given point of an ellipse, can be controlled by the Kolmogorov width of a set similarly localized. This connection leads to an explicit characterization of the estimation error of least-squares regression as a function of the true regression vector within the ellipse. The rate of error decay varies substantially as a function of location: as a concrete example, in Sobolev ellipses of smoothness $α$, we exhibit rates that vary from $(σ^2)^{\frac{2 α}{2 α+ 1}}$, corresponding to the classical global rate, to the faster rate $(σ^2)^{\frac{4 α}{4 α+ 1}}$. We also show how the local Kolmogorov width can be related to local metric entropy.
此内容由惯性聚合(RSS阅读器)自动聚合整理,仅供阅读参考。 原文来自 — 版权归原作者所有。