Refined regularity at critical points for linear elliptic equations

Fuente: arXiv
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Autores principales: Choi, Jongkeun, Dong, Hongjie, Kim, Seick
Formato: Preprint
Publicado: 2025
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author Choi, Jongkeun
Dong, Hongjie
Kim, Seick
author_facet Choi, Jongkeun
Dong, Hongjie
Kim, Seick
contents We investigate the regularity of solutions to linear elliptic equations in both divergence and non-divergence forms, particularly when the principal coefficients have Dini mean oscillation. We show that if a solution $u$ to a divergence-form equation satisfies $Du(x^o)=0$ at a point, then the second derivative $D^2u(x^o)$ exists and satisfies sharp continuity estimates. As a consequence, we obtain ``$C^{2,α}$ regularity'' at critical points when the coefficients of $L$ are $C^α$. This result refines a theorem of Teixeira (Math. Ann. 358 (2014), no. 1--2, 241--256) in the linear setting, where both linear and nonlinear equations were considered. We also establish an analogous result for equations in non-divergence form.
format Preprint
id arxiv_https___arxiv_org_abs_2506_08281
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Refined regularity at critical points for linear elliptic equations
Choi, Jongkeun
Dong, Hongjie
Kim, Seick
Analysis of PDEs
We investigate the regularity of solutions to linear elliptic equations in both divergence and non-divergence forms, particularly when the principal coefficients have Dini mean oscillation. We show that if a solution $u$ to a divergence-form equation satisfies $Du(x^o)=0$ at a point, then the second derivative $D^2u(x^o)$ exists and satisfies sharp continuity estimates. As a consequence, we obtain ``$C^{2,α}$ regularity'' at critical points when the coefficients of $L$ are $C^α$. This result refines a theorem of Teixeira (Math. Ann. 358 (2014), no. 1--2, 241--256) in the linear setting, where both linear and nonlinear equations were considered. We also establish an analogous result for equations in non-divergence form.
title Refined regularity at critical points for linear elliptic equations
topic Analysis of PDEs
url https://arxiv.org/abs/2506.08281