activity
20192026
collaborators

10 papers

math.ST2026

The joint density of top k sample eigenvectors and principal subspace inference

Koki Shimizu, Haoming Wang

In this paper, the exact joint density of the top sample eigenvectors is derived for any population covariance matrix , sample size , and $1 \l…

math.ST2026

Multivariate normality test based on the uniform distribution on the Stiefel manifold

Koki Shimizu, Toshiya Iwashita

This study presents a new procedure for necessary tests of multivariate normality based on the uniform distribution on the Stiefel manifold. We demonstrate that the test statistic,…

stat.ML2025

Evaluating Singular Value Thresholds for DNN Weight Matrices based on Random Matrix Theory

Kohei Nishikawa, Koki Shimizu, Hiroki Hashiguchi

This study evaluates thresholds for removing singular values from singular value decomposition-based low-rank approximations of deep neural network weight matrices. Each weight mat…

math.ST2025

Exact Distribution of the Noncentral Complex Roy's Largest Root Statistic via Pieri's Formula

Koki Shimizu, Hiroki Hashiguchi

In this study, we derive the exact distribution and moment of the noncentral complex Roy's largest root statistic, expressed as a product of complex zonal polynomials. We show that…

math.ST2023

Chi-square approximation for the distribution of individual eigenvalues of a singular Wishart matrix

Koki Shimizu, Hiroki Hashiguchi

This paper discusses the approximate distributions of eigenvalues of a singular Wishart matrix. We give the approximate joint density of eigenvalues by Laplace approximation for th…

math.ST2022

Numerical computation for the exact distribution of Roy's largest root statistic under linear alternative

Koki Shimizu, Hiroki Hashiguchi

This paper discusses the computation of exact powers for Roy's test in multivariate analysis of variance~(MANOVA). We derive an exact expression for the largest eigenvalue of a sin…

math.ST2021

Algorithm for the product of Jack polynomials and its application to the sphericity test

Koki Shimizu, Hiroki Hashiguchi

In this study, we derive the density and distribution function of a ratio of the largest and smallest eigenvalues of a singular beta-Wishart matrix for the sphericity test. These f…

math.ST2021

Generalized heterogeneous hypergeometric functions and the distribution of the largest eigenvalue of an elliptical Wishart matrix

Aya Shinozaki, Koki Shimizu, Hiroki Hashiguchi

In this study, we derive the exact distributions of eigenvalues of a singular Wishart matrix under an elliptical model. We define generalized heterogeneous hypergeometric functions…

math.ST2020

Expressing the largest eigenvalue of a singular beta F-matrix with heterogeneous hypergeometric functions

Koki Shimizu, Hiroki Hashiguchi

In this paper, the exact distribution of the largest eigenvalue of a singular random matrix for multivariate analysis of variance (MANOVA) is discussed. The key to developing the d…

math.ST2019

Heterogeneous hypergeometric functions with two matrix arguments and the exact distribution of the largest eigenvalue of a singular beta-Wishart matrix

Koki Shimizu, Hiroki Hashiguchi

This paper discusses certain properties of heterogeneous hypergeometric functions with two matrix arguments. These functions are newly defined but have already appeared in statisti…