Electron. J. Differential Equations, Vol. 2026 (2026), No. 67, pp. 1-31.

Existence and uniqueness of solutions for compressible magnetohydrodynamic equations with bounded density

Yasi Zheng

Abstract:
This article concerns the three-dimensional compressible magnetohydrodynamic equations on the torus in the presence of vacuum. We establish the existence and uniqueness of strong local solutions for low-regularity initial data without imposing an initial compatibility condition. More precisely, the initial data are assumed to satisfy \(0\leq \rho_0\in L^\infty(\mathbb T^3), u_0,b_0\in H^1(\mathbb T^3), \text{div}b_0=0\). The main difficulties arise from the strong nonlinear coupling between the velocity and magnetic field and from the low regularity of the density. By introducing the effective viscous flux and deriving suitable time-weighted energy estimates, we establish a uniform local existence theory independent of the initial compatibility condition. For uniqueness, we estimate the density difference in a negative Sobolev space and introduce a coupled backward parabolic system to avoid derivatives of the density. The proof is completed by a logarithmic BMO estimate and an Osgood-type argument.

Submitted June 18, 2026. Published September 3, 2026.
Math Subject Classifications: 35D35, 76N10, 76W05.
Key Words: Compressible magnetohydrodynamic equations; existence and uniqueness; effective viscous flux; logarithmic Gronwall inequality
DOI: 10.58997/ejde.2026.67

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Yasi Zheng
Institute of Applied Mathematics
Shenzhen Polytechnic University
Shenzhen 518055, China
email: yszheng@szpu.edu.cn

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