Polyconvex double well functions

Fuente: arXiv
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Auteurs principaux: Henrion, Didier, Kružík, Martin
Format: Preprint
Publié: 2025
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author Henrion, Didier
Kružík, Martin
author_facet Henrion, Didier
Kružík, Martin
contents We investigate polyconvexity of the double well function $f(X)\,:= |X-X\_1|^2|X-X\_2|^2$ for given matrices $X\_1, X\_2 \in \R^{n \times n}$. Such functions are fundamental in the modeling of phase transitions in materials, but their non-convex nature presents challenges for the analysis of variational problems. Polyconvexity of $f$ is related to the singular values of the matrix difference $X\_1 - X\_2$. We prove that $f$ is polyconvex if and only if the square of the largest singular value does not exceed the sum of the squares of the other singular values. This condition allows the function to be decomposed into the sum of a strictly convex part and a null Lagrangean. As a direct application of this result, we prove an existence and uniqueness theorem for the corresponding Dirichlet minimization problem of the integral functional.
format Preprint
id arxiv_https___arxiv_org_abs_2508_14541
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Polyconvex double well functions
Henrion, Didier
Kružík, Martin
Optimization and Control
We investigate polyconvexity of the double well function $f(X)\,:= |X-X\_1|^2|X-X\_2|^2$ for given matrices $X\_1, X\_2 \in \R^{n \times n}$. Such functions are fundamental in the modeling of phase transitions in materials, but their non-convex nature presents challenges for the analysis of variational problems. Polyconvexity of $f$ is related to the singular values of the matrix difference $X\_1 - X\_2$. We prove that $f$ is polyconvex if and only if the square of the largest singular value does not exceed the sum of the squares of the other singular values. This condition allows the function to be decomposed into the sum of a strictly convex part and a null Lagrangean. As a direct application of this result, we prove an existence and uniqueness theorem for the corresponding Dirichlet minimization problem of the integral functional.
title Polyconvex double well functions
topic Optimization and Control
url https://arxiv.org/abs/2508.14541