The possible inertias for a Hermitian matrix and its principal submatrices
type: Item
instance of: scholarly article
title: The possible inertias for a Hermitian matrix and its principal submatrices
zbMATH Open document ID: 0614.15011
DOI: 10.1016/0024-3795(87)90212-6
author: Jerome Dancis
published in: Linear Algebra and its Applications
publication date: 1987-01-01T00:00:00Z
review text: Let \(H_{ii}\) be \(n_ i\times n_ i\) Hermitian matrices, \(i=1,2,...,m\), \((\pi_ i,\nu_ i,\delta_ i)=In H_{ii}\), the inertia of \(H_{ii}\) where \(\pi_ i\), \(\nu_ i\), \(\delta_ i\) are the numbers of positive, negative and zero eigenvalues of \(H_{ii}\) correspondingly, \(n=\sum^{m}_{i=1}n_ i\). The author calls an \(n\times n\)-Hermitian matrix H a Hermitian extension of the \(H_{ii}'s\) if the \(H_{ii}'s\) are the block diagonals of H. The objective of the paper is the study of relations between \((\pi_ i,\nu_ i,\delta_ i)\) and In H, the inertia of H. Examples of the results proved in the paper: 1) Given nonnegative integers \(\pi\), \(\nu\), \(\delta\) such that \(\pi +\nu +\delta =\sum (\pi_ i+\nu_ i+\delta_ i)\); a Hermitian extension H of \(\{H_{ii}\}\) such that Ker \(H\supset \oplus Ker H_{ii}\) and In H\(=(\pi,\nu,\delta)\) exists iff \(\delta\geq \sum \delta_ i\), \(\pi\geq \max \pi_ i\), \(\nu\geq \max \nu_ i\) (corollary 1.1); 2) A Hermitian extension H of \(\{H_{ii}\}\) such that Ker H/C\({}^{n_ i}=\{\bar O\}\) where \(C^{n_ i}\) is the domain of \(H_{ii}\), \(i=1,2,...,m\) exists iff \(\pi \geq \max (\pi_ i+\delta_ i)\), \(\nu \geq \max (\nu_ i+\delta_ i)\) (corollary 1.2).
Mathematics Subject Classification ID: 15B57
Mathematics Subject Classification ID: 15A18
Mathematics Subject Classification ID: 15A63
zbMATH DE Number: 3993771
zbMATH Keywords: Hermitian matrices
zbMATH Keywords: inertia
zbMATH Keywords: Hermitian extension
reviewed by: Boris Raykhshteyn
MaRDI profile type: Publication
full work available at URL: 0024-3795(87)90212-6
OpenAlex ID: W1993283237
cites work: On the inertia of sums of Hermitian matrices
cites work: The inertia of a Hermitian matrix having prescribed complementary principal submatrices
cites work: The inertia of a Hermitian matrix having prescribed diagonal blocks
cites work: On the inertias of symmetric matrices and bounded self-adjoint operators
cites work: Inertia possibilities for completions of partial hermitian matrices*
description: scientific article; zbMATH DE number 3993771