Non-constant functions with zero nonlocal gradient and their role in nonlocal Neumann-type problems

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Hauptverfasser: Kreisbeck, Carolin, Schönberger, Hidde
Format: Preprint
Veröffentlicht: 2024
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author Kreisbeck, Carolin
Schönberger, Hidde
author_facet Kreisbeck, Carolin
Schönberger, Hidde
contents This work revolves around properties and applications of functions whose nonlocal gradient, or more precisely, finite-horizon fractional gradient, vanishes. Surprisingly, in contrast to the classical local theory, we show that this class forms an infinite-dimensional vector space. Our main result characterizes the functions with zero nonlocal gradient in terms of two simple features, namely, their values in a layer around the boundary and their average. The proof exploits recent progress in the solution theory of boundary-value problems with pseudo-differential operators. We complement these findings with a discussion of the regularity properties of such functions and give illustrative examples. Regarding applications, we provide several useful technical tools for working with nonlocal Sobolev spaces when the common complementary-value conditions are dropped. Among these, are new nonlocal Poincaré inequalities and compactness statements, which are obtained after factoring out functions with vanishing nonlocal gradient. Following a variational approach, we exploit the previous findings to study a class of nonlocal partial differential equations subject to natural boundary conditions, in particular, nonlocal Neumann-type problems. Our analysis includes a proof of well-posedness and a rigorous link with their classical local counterparts via $Γ$-convergence as the fractional parameter tends to 1.
format Preprint
id arxiv_https___arxiv_org_abs_2402_11308
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Non-constant functions with zero nonlocal gradient and their role in nonlocal Neumann-type problems
Kreisbeck, Carolin
Schönberger, Hidde
Analysis of PDEs
35R11, 49J45 (Primary) 47G20, 35S15, 46E35 (Secondary)
This work revolves around properties and applications of functions whose nonlocal gradient, or more precisely, finite-horizon fractional gradient, vanishes. Surprisingly, in contrast to the classical local theory, we show that this class forms an infinite-dimensional vector space. Our main result characterizes the functions with zero nonlocal gradient in terms of two simple features, namely, their values in a layer around the boundary and their average. The proof exploits recent progress in the solution theory of boundary-value problems with pseudo-differential operators. We complement these findings with a discussion of the regularity properties of such functions and give illustrative examples. Regarding applications, we provide several useful technical tools for working with nonlocal Sobolev spaces when the common complementary-value conditions are dropped. Among these, are new nonlocal Poincaré inequalities and compactness statements, which are obtained after factoring out functions with vanishing nonlocal gradient. Following a variational approach, we exploit the previous findings to study a class of nonlocal partial differential equations subject to natural boundary conditions, in particular, nonlocal Neumann-type problems. Our analysis includes a proof of well-posedness and a rigorous link with their classical local counterparts via $Γ$-convergence as the fractional parameter tends to 1.
title Non-constant functions with zero nonlocal gradient and their role in nonlocal Neumann-type problems
topic Analysis of PDEs
35R11, 49J45 (Primary) 47G20, 35S15, 46E35 (Secondary)
url https://arxiv.org/abs/2402.11308