🤖 AI Summary
High-dimensional data often exhibit heavy tails, heterogeneity, and non-Gaussian characteristics, which undermine the validity of conventional covariance-based methods. This work proposes a unified robust inference framework tailored to elliptically symmetric distributions, integrating techniques such as spatial signs, spatial ranks, multivariate Kendall’s tau matrices, shape matrix estimation, and adaptive testing. By relaxing the restrictive Gaussian assumption, the framework achieves robust and efficient performance across a range of high-dimensional tasks—including location inference, covariance and precision matrix estimation, factor model testing, discriminant analysis, and dimension reduction—thereby substantially enhancing adaptability to heavy-tailed high-dimensional data.
📝 Abstract
High-dimensional data arise routinely in modern statistics, econometrics, finance, genomics, and machine learning. While a large body of existing methodology is developed under Gaussian or light-tailed assumptions, many real data sets exhibit heavy tails, heterogeneity, and departures from classical covariance-based models. This book provides a systematic treatment of high-dimensional data analysis under elliptically symmetric distributions, with an emphasis on robust inference based on spatial signs, spatial ranks, multivariate Kendall's tau matrices, and related shape-based methods.The book covers the basic theory of elliptical symmetry, high-dimensional location inference, estimation and testing for covariance and precision matrices, sphericity and proportionality testing, high-dimensional alpha testing in factor pricing models, change-point analysis, white-noise and independence testing, high-dimensional discriminant analysis, and dimension reduction through principal component analysis and factor models. Throughout, we review classical low-dimensional and high-dimensional benchmark methods and then develop robust alternatives tailored to elliptical models. Particular attention is paid to the interplay between sum-type, max-type, and adaptive procedures, as well as to the role of scatter, shape, and rank-based dependence measures in heavy-tailed settings. This book is intended as a unified overview of robust high-dimensional methods under elliptical symmetry and as a synthesis of the author's recent research contributions in this area. It is written for researchers and graduate students in statistics, econometrics, and related fields who are interested in modern high-dimensional inference beyond the Gaussian paradigm.