# A Note on Kantorovich Inequality for Hermite Matrices

- Zhibing Liu
^{1, 2}Email author, - Kanmin Wang
^{2}and - Chengfeng Xu
^{2}

**2011**:245767

https://doi.org/10.1155/2011/245767

© Zhibing Liu et al. 2011

**Received: **10 November 2010

**Accepted: **19 February 2011

**Published: **13 March 2011

## Abstract

A new Kantorovich type inequality for Hermite matrices is proposed in this paper. It holds for the invertible Hermite matrices and provides refinements of the classical results. Elementary methods suffice to prove the inequality.

## 1. Introduction

This famous inequality plays an important role in statistics and numerical analysis, for example, in discussions of converging rates and error bounds of solving systems of equations (see [2–4]). Motivated by interests in applied mathematics outlined above, we establish in this paper a new Kantorovich type inequality, the classical Kantorovich inequality is modified to apply not only to positive definite but also to all invertible Hermitian matrices. An elementary proof of this result is also presented.

In the next section, we will state the main theorem and its proof. Before starting, we quickly review some basic definitions and notations. Let be an invertible Hermite matrix with real eigenvalues , and the corresponding orthonormal eigenvectors with , where denotes 2-norm of the vector of .

## 2. New Kantorovich Inequality for Hermite Matrices

Theorem 2.1.

for any , , where , , , defined by (1.3), (1.4), (1.5), and (1.6).

To simplify the proof, we first introduce some lemmas.

Lemma 2.2.

Lemma 2.3.

Proof.

Lemma 2.4.

Proof.

The other inequality can be obtained similarly, the proof is completed.

We are now ready to prove the theorem.

Proof.

The proof of Theorem 2.1 is completed.

Remark 2.5.

our result improves the Kantorovich inequality (1.2), so we conclude that Theorem 2.1 gives an improvement of the Kantorovich inequality that applies all invertible Hermite matrices.

Example 2.6.

we get a sharpen upper bound.

## 3. Conclusion

In this paper, we introduce a new Kantorovich type inequality for the invertible Hermite matrices. In Theorem 2.1, if , , the result is well-known Kantorovich inequality. Moreover, it holds for negative definite Hermite matrices, even for any invertible Hermite matrix, there exists a similar inequality.

## Declarations

### Acknowledgments

The authors would like to thank the two anonymous referees for their valuable comments which have been implemented in this revised version. This work is supported by Natural Science Foundation of Jiangxi, China No 2007GZS1760 and scienctific and technological project of Jiangxi education office, China No GJJ08432.

## Authors’ Affiliations

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## Copyright

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.