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非电阻性或非粘性MHD系统的全局正则性

Global Regularity for Non-resistive or Non-viscous MHD System on the Torus

School of Mathematical Sciences, Capital Normal University(首都师范大学数学科学学院)

Quansen Jiu, Yaowei Xie, Zhihong Yan

AI总结:

本文研究了非电阻性或非粘性MHD系统在周期域上的全局正则性,通过时间加权能量估计和交换子估计,证明了在不同初始对称性假设下的适定性,并展示了磁场对非粘性MHD系统中潜在爆破机制的抑制作用。

摘要:

本文中,我们在n维(n≥2)周期盒上建立了不可压缩磁流体动力学(MHD)系统的全局适定性,假设初始磁场足够接近背景磁场e_n=(0,⋯,0,1)。在欧拉坐标下,我们开发了新型的时间加权能量估计和涉及负Sobolev空间中的Riesz变换的交换子估计,以处理两种不同的耗散情况,且在不同的初始对称性假设下。在三维或更高维的情况下,分析变得更加困难和精细。特别是,在三维且非电阻性的情况下,与Pan、Zhou和Zhu [Arch. Ration. Mech. Anal. 2018] 提出的正则性要求相比,我们的结果将其从H^{11}(T^3)放松到H^{9/2+}(T^3)。我们进一步建立了u(t)和∂_n(u(t),b(t))在Sobolev范数中的精确衰减率和增长界。在三维且非粘性的情况下,我们证明了在背景场e_3=(0,0,1)附近的第一非线性稳定性结果。这与最近关于3D不可压缩欧拉方程的爆破结果形成鲜明对比,如Elgindi [Ann. Math. 2021]、Chen-Hou [Commun. Math. Phys. 2021] 和Chen-Hou [arXiv:2210.07191]。我们的结果表明,在某些对称性假设下,接近背景场的磁场提供了增强的耗散并抑制了非粘性MHD系统中的潜在爆破机制。

英文摘要:

In this paper, we establish the global well-posedness of the incompressible magnetohydrodynamics (MHD) system on $n-$dimensional $(n\geq 2)$ periodic boxes with either no magnetic diffusivity (non-resistive case) or no fluid viscosity (non-viscous case) under assumption that initial magnetic fields are sufficiently close to the background magnetic field ${\bf e}_n=(0,\cdots,0,1)$. In Eulerian coordinates, we develop novel time-weighted energy estimates and commutator estimates involving Riesz transforms in negative Sobolev spaces to handle two distinct dissipation cases under different initial symmetry assumptions. The analysis becomes much more difficult and delicate in three- or higher-dimensional cases. In particular, for the three-dimensional and non-resistive case, compared with the regularity requirement proposed by Pan, Zhou and Zhu {\it [Arch. Ration. Mech. Anal. 2018]}, our result relaxes it from $H^{11}(\mathbb{T}^3)$ to $H^{\frac{9}{2}+}(\mathbb{T}^3)$. And we further establish precise decay rates and growth bounds for both $u(t)$ and $\partial_n(u(t),b(t))$ in Sobolev norms. For the three-dimensional and non-viscous case, we prove the first nonlinear stability result near the background field $\mathbf{e}_3 = (0,0,1)$. This sharply contrasts with the recent blow-up results on the 3D incompressible Euler equations by Elgindi {\it [Ann. Math. 2021]}, Chen-Hou {\it [Commun. Math. Phys. 2021]} and by Chen-Hou {\it [arXiv:2210.07191]}. Our results show that, under certain symmetry assumptions, magnetic fields near the background field provide enhanced dissipations and suppress potential blow-up mechanisms in non-viscous MHD system.

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