Generic topological screening and approximation of Sobolev maps

Fuente: arXiv
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Main Authors: Bousquet, Pierre, Ponce, Augusto C., Van Schaftingen, Jean
Format: Preprint
Published: 2025
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author Bousquet, Pierre
Ponce, Augusto C.
Van Schaftingen, Jean
author_facet Bousquet, Pierre
Ponce, Augusto C.
Van Schaftingen, Jean
contents This manuscript develops a framework for the strong approximation of Sobolev maps with values in compact manifolds, emphasizing the interplay between local and global topological properties. Building on topological concepts adapted to VMO maps, such as homotopy and the degree of continuous maps, it introduces and analyzes extendability properties, focusing on the notions of $\ell$-extendability and its generalization, $(\ell, e)$-extendability. We rely on Fuglede maps, providing a robust setting for handling compositions with Sobolev maps. Several constructions -- including opening, thickening, adaptive smoothing, and shrinking -- are carefully integrated into a unified approach that combines homotopical techniques with precise quantitative estimates. Our main results establish that a Sobolev map $u \in W^{k, p}$ defined on a compact manifold of dimension $m > kp$ can be approximated by smooth maps if and only if $u$ is $(\lfloor kp \rfloor, e)$-extendable with $e = m$. When $e < m$, the approximation can still be carried out using maps that are smooth except on structured singular sets of rank $m - e - 1$.
format Preprint
id arxiv_https___arxiv_org_abs_2501_18149
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Generic topological screening and approximation of Sobolev maps
Bousquet, Pierre
Ponce, Augusto C.
Van Schaftingen, Jean
Functional Analysis
Analysis of PDEs
Classical Analysis and ODEs
Primary: 58D15, 46E35, 58C25, Secondary: 47H11, 26A99, 55S35
This manuscript develops a framework for the strong approximation of Sobolev maps with values in compact manifolds, emphasizing the interplay between local and global topological properties. Building on topological concepts adapted to VMO maps, such as homotopy and the degree of continuous maps, it introduces and analyzes extendability properties, focusing on the notions of $\ell$-extendability and its generalization, $(\ell, e)$-extendability. We rely on Fuglede maps, providing a robust setting for handling compositions with Sobolev maps. Several constructions -- including opening, thickening, adaptive smoothing, and shrinking -- are carefully integrated into a unified approach that combines homotopical techniques with precise quantitative estimates. Our main results establish that a Sobolev map $u \in W^{k, p}$ defined on a compact manifold of dimension $m > kp$ can be approximated by smooth maps if and only if $u$ is $(\lfloor kp \rfloor, e)$-extendable with $e = m$. When $e < m$, the approximation can still be carried out using maps that are smooth except on structured singular sets of rank $m - e - 1$.
title Generic topological screening and approximation of Sobolev maps
topic Functional Analysis
Analysis of PDEs
Classical Analysis and ODEs
Primary: 58D15, 46E35, 58C25, Secondary: 47H11, 26A99, 55S35
url https://arxiv.org/abs/2501.18149