论文标题
在代数和统计的界面上
At the Interface of Algebra and Statistics
论文作者
论文摘要
本论文从量子物理学中汲取灵感来研究代数和统计界面的数学结构。起点是从经典概率理论到量子概率理论的段落。概率分布的量子版本是密度运算符,边缘化的量子版本是一个称为部分跟踪的操作,边际概率分布的量子版本是降低的密度运算符。有限集中的每个关节概率分布都可以建模为等级一密度运算符。通过应用部分迹线,我们获得了降低的密度算子,其对角线恢复了经典的边缘概率。通常,这些降低的密度将高于1的排名,其特征值和特征向量将包含额外的信息,该信息编码由统计数据控制的子系统相互作用。我们对此信息进行了解码,并表明它类似于条件概率,然后研究特征向量捕获原始关节分布中固有的“概念”的程度。然后,通过利用这些想法的实验来说明该理论。转向更理论上的应用,我们还讨论了一种以自然语言建模和概念层次结构的初步框架,即通过表示语言的表达方式为密度。最后,本论文的最初灵感来自正式的概念分析,这与线性代数相似。相似之处不是偶然的,并且在类别理论中发现了共同的蓝图。我们以自由(CO)完成的说明以及它们出现的自由验证辅助作用而结束,这强烈表明,在某些分类环境中,词性的“固定点”具有其伴随编码有趣的信息。
This thesis takes inspiration from quantum physics to investigate mathematical structure that lies at the interface of algebra and statistics. The starting point is a passage from classical probability theory to quantum probability theory. The quantum version of a probability distribution is a density operator, the quantum version of marginalizing is an operation called the partial trace, and the quantum version of a marginal probability distribution is a reduced density operator. Every joint probability distribution on a finite set can be modeled as a rank one density operator. By applying the partial trace, we obtain reduced density operators whose diagonals recover classical marginal probabilities. In general, these reduced densities will have rank higher than one, and their eigenvalues and eigenvectors will contain extra information that encodes subsystem interactions governed by statistics. We decode this information, and show it is akin to conditional probability, and then investigate the extent to which the eigenvectors capture "concepts" inherent in the original joint distribution. The theory is then illustrated with an experiment that exploits these ideas. Turning to a more theoretical application, we also discuss a preliminary framework for modeling entailment and concept hierarchy in natural language, namely, by representing expressions in the language as densities. Finally, initial inspiration for this thesis comes from formal concept analysis, which finds many striking parallels with the linear algebra. The parallels are not coincidental, and a common blueprint is found in category theory. We close with an exposition on free (co)completions and how the free-forgetful adjunctions in which they arise strongly suggest that in certain categorical contexts, the "fixed points" of a morphism with its adjoint encode interesting information.