arXiv subjects

Daniel Gourion

Publications and source records attributed to Daniel Gourion.

2 recordsLinked to original sources

arXiv2025

The maximal angle between $3 \times 3$ copositive matrices

In 2010, Hiriart-Urruty and Seeger posed the problem of finding the maximal possible angle $\theta_n$ between two copositive matrices of order $n$. They proved that $\theta_2=\frac{3}{4}\pi$. In this paper, we study the maximal angle between two copositive matrices of order 3. We show that $\theta_3=\frac{3}{4}\pi$ 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.

math.OC↗

arXiv2021

An upper bound for the number of chess diagrams without promotion

In 2015, Steinerberger showed that the number of legal chess diagrams without promotion is bounded from above by $2\times 10^{40}$. This number was obtained by restricting both bishops and pawns position and by a precise bound when no chessman has been captured. We improve this estimate and show that the number of legal diagrams is less than $4\times 10^{37}$. To achieve this, we define a graph on the set of diagrams and a notion of class of pawn arrangements, leading to a method for bounding pawn positions with any number of men on the board.

cs.GT↗