arXiv:2505.04613stat.MLcs.LG2025-05被引 4

证明核嵌入能让不同概率分布完全分离,为核方法提供理论支持。

Kernel Embeddings and the Separation of Measure Phenomenon

  • 用核协方差嵌入将概率分布映射到希尔伯特空间中的高斯测度。
  • 在无限维空间中,不同分布的嵌入高斯测度本质分离,可完美区分。
  • 适用于高维复杂数据的高效统计推断设计,尤其适合核方法研究者。

我们证明,核协方差嵌入能实现信息论意义上的不同连续概率分布的完全分离。从统计学角度看,在局部紧致不可数波兰空间上,测试两个非原子(Borel)概率测度是否相等,等价于测试两个中心高斯测度在再生核希尔伯特空间中的奇异关系。这些高斯测度由概率测度的核协方差嵌入定义,其希尔伯特空间由嵌入核生成。在信息论视角下,区分奇异高斯测度比非参数两样本检验更简单,特别是在复杂或高维域中,因为奇异高斯测度支撑在本质上分离且仿射的子空间上。证明依赖经典Feldman-Hájek二分性,表明即使对连续分布进行微小扰动,也会在其高斯嵌入中被极大放大。这一‘测度分离现象’似乎是无限维嵌入带来的优势,具有广泛启发意义,可指导高效推断工具的设计。该现象的揭示也以精确简洁的数学形式,凝练了核方法经验有效性的核心机制。

原文摘要 · Abstract (English)

We prove that kernel covariance embeddings lead to information-theoretically perfect separation of distinct continuous probability distributions. In statistical terms, we establish that testing for the \emph{equality} of two non-atomic (Borel) probability measures on a locally compact uncountable Polish space is \emph{equivalent} to testing for the \emph{singularity} between two centered Gaussian measures on a reproducing kernel Hilbert space. The corresponding Gaussians are defined via the notion of kernel covariance embedding of a probability measure, and the Hilbert space is that generated by the embedding kernel. Distinguishing singular Gaussians is structurally simpler from an information-theoretic perspective than non-parametric two-sample testing, particularly in complex or high-dimensional domains. This is because singular Gaussians are supported on essentially separate and affine subspaces. Our proof leverages the classical Feldman-Hájek dichotomy, and shows that even a small perturbation of a continuous distribution will be maximally magnified through its Gaussian embedding. This ``separation of measure phenomenon'' appears to be a blessing of infinite dimensionality, by means of embedding, with the potential to inform the design of efficient inference tools in considerable generality. The elicitation of this phenomenon also appears to crystallize, in a precise and simple mathematical statement, a core mechanism underpinning the empirical effectiveness of kernel methods.

核方法概率分布高维统计嵌入理论

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