Electron. J. Differential Equations, Vol. 2026 (2026), No. 29, pp. 1-22.

Gradient continuity of local minimizers of a borderline double-phase functional with DMO coefficients

Wenrui Chang, Yuxia Tong, Shenzhou Zheng

Abstract:
Let \(u \in W^{1,1}(\Omega)\). We study a local gradient continuity of the minimizers of functionals with borderline double-phase growth, $$ \mathcal{F}(u ; \Omega) := \int_{\Omega} \Big(|Du|_\mathbb{A}^{p} + a(x)\, |Du|^{p}_\mathbb{A} \log(e + |Du|_\mathbb{A})\Big) \,dx $$ for \(1 < p < \infty\) and \(|Du|_{\mathbb{A}} :=\langle \mathbb{A}(x) Du, Du \rangle^{1/2}\), where the matrix \(\mathbb{A}(x) = \{A^{\alpha \beta}(x)\}\) is symmetric with positive upper and lower bounds of its eigenvalues. We prove that \(Du\in C^1_{\rm loc}(\Omega)\) based mainly on the exit-time approach, provided that the moderating factor \(a(x)\) and coefficient \(\mathbb{A}(x)\) satisfy the so-called Dini-type mean oscillation conditions.

Submitted November 28, 2025. Published April 27, 2026.
Math Subject Classifications: 35B65, 35J15, 35J60.
Key Words: Gradient continuity; non-autonomous functional; Dini mean oscillation; borderline double phase.
DOI: 10.58997/ejde.2026.29

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Wenrui Chang
School of Mathematics and Statistics
Beijing Jiaotong University
Beijing 100044, China
email: wenruichang@bjtu.edu.cn
Yuxia Tong
School of Mathematics and Statistics
North China University of Science and Technology
Tangshan 063210, China
email: tongyuxia@126.com
Shenzhou Zheng
School of Mathematics and Statistics
Beijing Jiaotong University
Beijing 100044, China
email: shzhzheng@bjtu.edu.cn

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