Generalizing the Cauchy-Schwarz inequality: Hadamard powers and tensor products

Fuente: arXiv
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Hauptverfasser: Johnston, Nathaniel, Plosker, Sarah, Torrance, Charles, Varona, Luis M. B.
Format: Preprint
Veröffentlicht: 2025
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author Johnston, Nathaniel
Plosker, Sarah
Torrance, Charles
Varona, Luis M. B.
author_facet Johnston, Nathaniel
Plosker, Sarah
Torrance, Charles
Varona, Luis M. B.
contents We explore and generalize a Cauchy-Schwarz-type inequality originally proved in [Electronic Journal of Linear Algebra 35, 156-180 (2019)]: $\|\mathbf{v}^2\|\|\mathbf{w}^2\| - \langle\mathbf{v}^2,\mathbf{w}^2\rangle \leq \|\mathbf{v}\|^2\|\mathbf{w}\|^2 - \langle\mathbf{v},\mathbf{w}\rangle^2$ for all $\mathbf{v},\mathbf{w} \in \mathbb{R}^n$. We present three new proofs of this inequality that better illustrate "why" it is true and generalize it in several different ways: we generalize from vectors to matrices, we explore which exponents other than 2 result in the inequality holding, and we derive a version of the inequality involving three or more vectors.
format Preprint
id arxiv_https___arxiv_org_abs_2507_10327
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Generalizing the Cauchy-Schwarz inequality: Hadamard powers and tensor products
Johnston, Nathaniel
Plosker, Sarah
Torrance, Charles
Varona, Luis M. B.
Functional Analysis
Quantum Physics
We explore and generalize a Cauchy-Schwarz-type inequality originally proved in [Electronic Journal of Linear Algebra 35, 156-180 (2019)]: $\|\mathbf{v}^2\|\|\mathbf{w}^2\| - \langle\mathbf{v}^2,\mathbf{w}^2\rangle \leq \|\mathbf{v}\|^2\|\mathbf{w}\|^2 - \langle\mathbf{v},\mathbf{w}\rangle^2$ for all $\mathbf{v},\mathbf{w} \in \mathbb{R}^n$. We present three new proofs of this inequality that better illustrate "why" it is true and generalize it in several different ways: we generalize from vectors to matrices, we explore which exponents other than 2 result in the inequality holding, and we derive a version of the inequality involving three or more vectors.
title Generalizing the Cauchy-Schwarz inequality: Hadamard powers and tensor products
topic Functional Analysis
Quantum Physics
url https://arxiv.org/abs/2507.10327