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Main Authors: Kim, Kyeongbae, Nowak, Simon, Sire, Yannick
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2602.15715
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author Kim, Kyeongbae
Nowak, Simon
Sire, Yannick
author_facet Kim, Kyeongbae
Nowak, Simon
Sire, Yannick
contents In this paper, we derive several regularity results for harmonic mappings into Euclidean spheres associated with rather general energies related to fractional Sobolev spaces. These maps generalize families of maps introduced by Da Lio, Rivière and Schikorra and are related to harmonic maps with free boundaries. In our context, there is in general no monotonicity formula, which prevents the use of some classical methods. Despite this limitation, under natural assumptions on a Gagliardo-type energy, we succeed in proving a variety of small energy regularity results and improve on known results, even in the isotropic case for which some monotonicity formula is available. To this end, we exploit recent developments in the regularity theory of nonlocal equations and as a by-product, we explain how these results apply to classes of harmonic maps with free boundary and lead to new potential-theoretic estimates. As another application, we obtain higher differentiability results for the fractional harmonic map heat flow.
format Preprint
id arxiv_https___arxiv_org_abs_2602_15715
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Fine regularity of fractional harmonic maps and applications
Kim, Kyeongbae
Nowak, Simon
Sire, Yannick
Analysis of PDEs
In this paper, we derive several regularity results for harmonic mappings into Euclidean spheres associated with rather general energies related to fractional Sobolev spaces. These maps generalize families of maps introduced by Da Lio, Rivière and Schikorra and are related to harmonic maps with free boundaries. In our context, there is in general no monotonicity formula, which prevents the use of some classical methods. Despite this limitation, under natural assumptions on a Gagliardo-type energy, we succeed in proving a variety of small energy regularity results and improve on known results, even in the isotropic case for which some monotonicity formula is available. To this end, we exploit recent developments in the regularity theory of nonlocal equations and as a by-product, we explain how these results apply to classes of harmonic maps with free boundary and lead to new potential-theoretic estimates. As another application, we obtain higher differentiability results for the fractional harmonic map heat flow.
title Fine regularity of fractional harmonic maps and applications
topic Analysis of PDEs
url https://arxiv.org/abs/2602.15715