论文标题
列表可解码的子空间恢复:多项式时间中的维度独立错误
List-Decodable Subspace Recovery: Dimension Independent Error in Polynomial Time
论文作者
论文摘要
在列表可解码的子空间恢复中,输入是$ n $点$αn$(对于某些$α\ ll 1/2 $)的集合,其中绘制了I.I.D.。从分配$ \ MATHCAL {D} $带有各向同性等级$ r $ r $协方差$π_*$(\ emph {inliers}),其余的都是任意的,潜在的对抗性异常值。目标是恢复$ O(1/α)$大小的候选协方差列表,其中包含$ \hatπ$接近$π_*$。最近的两项独立作品(Raghavendra-Yau,Bakshi-Kothari 2020)给出了第一个有效的算法。但是,这些结果会以符号 - 多溶液运行时间为代价的维度(在[ry]中线性和对数线性)而生长的错误,并依赖于\ emph {可认证的抗浓缩} - 相对严格的条件基本上仅由高斯分布来满足。 在这项工作中,我们在所有三个方面上都改进了这些结果:\ emph {dimension-nistepent}误差通过在较小的限制性分布假设下更快的固定溶态运行时间。具体来说,我们给出了$ poly(1/α)d^{o(1)} $ time算法,该算法输出包含满足$ \ | \hatπ -hatπ -hatπ_*_*\ | _f \ | _f \ leq O(1/α)$的列表。我们的结果只需要$ \ Mathcal {d} $才能具有\ emph {认证超合同}度2多项式。结果,除了高斯人之外,我们的算法还适用于HyperCube上的均匀分布,以及$ Q $ - Ary Cubes和Subgaussian边缘的任意产品分布。先前的工作(Raghavendra和Yau,2020年)已经确定了潜在的硬例子,因为这种分布没有表现出足够强的抗浓度。当$ \ mathcal {d} $满足可认证的反浓缩时,我们获得了$ \ | \hatπ-f \ | _f \ | _f \ | _f \ leq leqhη$的更强错误保证。
In list-decodable subspace recovery, the input is a collection of $n$ points $αn$ (for some $α\ll 1/2$) of which are drawn i.i.d. from a distribution $\mathcal{D}$ with a isotropic rank $r$ covariance $Π_*$ (the \emph{inliers}) and the rest are arbitrary, potential adversarial outliers. The goal is to recover a $O(1/α)$ size list of candidate covariances that contains a $\hatΠ$ close to $Π_*$. Two recent independent works (Raghavendra-Yau, Bakshi-Kothari 2020) gave the first efficient algorithm for this problem. These results, however, obtain an error that grows with the dimension (linearly in [RY] and logarithmically in BK) at the cost of quasi-polynomial running time) and rely on \emph{certifiable anti-concentration} - a relatively strict condition satisfied essentially only by the Gaussian distribution. In this work, we improve on these results on all three fronts: \emph{dimension-independent} error via a faster fixed-polynomial running time under less restrictive distributional assumptions. Specifically, we give a $poly(1/α) d^{O(1)}$ time algorithm that outputs a list containing a $\hatΠ$ satisfying $\|\hatΠ -Π_*\|_F \leq O(1/α)$. Our result only needs $\mathcal{D}$ to have \emph{certifiably hypercontractive} degree 2 polynomials. As a result, in addition to Gaussians, our algorithm applies to the uniform distribution on the hypercube and $q$-ary cubes and arbitrary product distributions with subgaussian marginals. Prior work (Raghavendra and Yau, 2020) had identified such distributions as potential hard examples as such distributions do not exhibit strong enough anti-concentration. When $\mathcal{D}$ satisfies certifiable anti-concentration, we obtain a stronger error guarantee of $\|\hatΠ-Π_*\|_F \leq η$ for any arbitrary $η> 0$ in $d^{O(poly(1/α) + \log (1/η))}$ time.