How smooth are restrictions of Besov functions?

Fuente: arXiv
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Main Author: Brasseur, Julien
Format: Preprint
Published: 2025
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author Brasseur, Julien
author_facet Brasseur, Julien
contents In a previous work, we showed that Besov spaces do not enjoy the restriction property unless $q\leq p$. Specifically, we proved that if $p<q$, then it is always possible to construct a function $f\in B_{p,q}^s(\mathbb{R}^N)$ such that $f(\cdot,y)\notin B_{p,q}^s(\mathbb{R}^d)$ for a.e. $y\in \mathbb{R}^{N-d}$, while this "pathology" does not happen if $q\leq p$. We showed that the partial maps belong, in fact, to the Besov space of generalised smoothness $B_{p,q}^{(s,Ψ)}(\mathbb{R}^d)$ provided the function $Ψ$ satisfies a simple summability condition involving $p$ and $q$. This short note completes the picture by showing that this characterisation is sharp.
format Preprint
id arxiv_https___arxiv_org_abs_2509_07420
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle How smooth are restrictions of Besov functions?
Brasseur, Julien
Functional Analysis
Analysis of PDEs
Classical Analysis and ODEs
In a previous work, we showed that Besov spaces do not enjoy the restriction property unless $q\leq p$. Specifically, we proved that if $p<q$, then it is always possible to construct a function $f\in B_{p,q}^s(\mathbb{R}^N)$ such that $f(\cdot,y)\notin B_{p,q}^s(\mathbb{R}^d)$ for a.e. $y\in \mathbb{R}^{N-d}$, while this "pathology" does not happen if $q\leq p$. We showed that the partial maps belong, in fact, to the Besov space of generalised smoothness $B_{p,q}^{(s,Ψ)}(\mathbb{R}^d)$ provided the function $Ψ$ satisfies a simple summability condition involving $p$ and $q$. This short note completes the picture by showing that this characterisation is sharp.
title How smooth are restrictions of Besov functions?
topic Functional Analysis
Analysis of PDEs
Classical Analysis and ODEs
url https://arxiv.org/abs/2509.07420