Periodic solutions to integro-differential equations: variational formulation, symmetry, and regularity

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Auteurs principaux: Cabre, Xavier, Csató, Gyula, Mas, Albert
Format: Preprint
Publié: 2024
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author Cabre, Xavier
Csató, Gyula
Mas, Albert
author_facet Cabre, Xavier
Csató, Gyula
Mas, Albert
contents We consider nonconstant periodic constrained minimizers of semilinear elliptic equations for integro-differential operators in $\mathbb{R}$. We prove that, after an appropriate translation, each of them is necessarily an even function which is decreasing in half its period. In particular, it has only two critical points in half its period, the absolute maximum and minimum. If these statements hold for all nonconstant periodic solutions, and not only for constrained minimizers, remains as an open problem. Our results apply to operators with kernels in two different classes: kernels $K$ which are convex and kernels for which $K(τ^{1/2})$ is a completely monotonic function of $τ$. This last new class arose in our previous work on nonlocal Delaunay surfaces in $\mathbb{R}^n$. Due to their symmetry of revolution, it gave rise to a 1d problem involving an operator with a nonconvex kernel. Our proofs are based on a not so well-known Riesz rearrangement inequality on the circle $\mathbb{S}^1$ established in 1976. We also put in evidence a new regularity fact which is a truly nonlocal-semilinear effect and also occurs in the nonperiodic setting. Namely, for nonlinearities in $C^β$ and when $2s+β<1$ ($2s$ being the order of the operator), the solution is not always $C^{2s+β-ε}$ for all $ε>0$.
format Preprint
id arxiv_https___arxiv_org_abs_2404_06462
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Periodic solutions to integro-differential equations: variational formulation, symmetry, and regularity
Cabre, Xavier
Csató, Gyula
Mas, Albert
Analysis of PDEs
35J61, 35B10, 35A15, 35S05
We consider nonconstant periodic constrained minimizers of semilinear elliptic equations for integro-differential operators in $\mathbb{R}$. We prove that, after an appropriate translation, each of them is necessarily an even function which is decreasing in half its period. In particular, it has only two critical points in half its period, the absolute maximum and minimum. If these statements hold for all nonconstant periodic solutions, and not only for constrained minimizers, remains as an open problem. Our results apply to operators with kernels in two different classes: kernels $K$ which are convex and kernels for which $K(τ^{1/2})$ is a completely monotonic function of $τ$. This last new class arose in our previous work on nonlocal Delaunay surfaces in $\mathbb{R}^n$. Due to their symmetry of revolution, it gave rise to a 1d problem involving an operator with a nonconvex kernel. Our proofs are based on a not so well-known Riesz rearrangement inequality on the circle $\mathbb{S}^1$ established in 1976. We also put in evidence a new regularity fact which is a truly nonlocal-semilinear effect and also occurs in the nonperiodic setting. Namely, for nonlinearities in $C^β$ and when $2s+β<1$ ($2s$ being the order of the operator), the solution is not always $C^{2s+β-ε}$ for all $ε>0$.
title Periodic solutions to integro-differential equations: variational formulation, symmetry, and regularity
topic Analysis of PDEs
35J61, 35B10, 35A15, 35S05
url https://arxiv.org/abs/2404.06462