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Bibliographic Details
Main Author: Gourion, Daniel
Format: Preprint
Published: 2025
Subjects:
Online Access:https://arxiv.org/abs/2501.03773
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Table of Contents:
  • In 2010, Hiriart-Urruty and Seeger posed the problem of finding the maximal possible angle $θ_n$ between two copositive matrices of order $n$. They proved that $θ_2=\frac{3}{4}π$. In this paper, we study the maximal angle between two copositive matrices of order 3. We show that $θ_3=\frac{3}{4}π$ and give all possible pairs of matrices achieving this maximal angle. The proof is based on case analysis and uses optimization and basic linear algebra techniques.