Nonlinear Partial Differential Equations and Applications

非线性偏微分方程及其应用研究建议摘要韩青在此奖项下，首席研究员计划继续他在偏微分方程方面的工作。特别是，他将研究微分方程解的节点集或更一般的水平函数集的作用。也讨论了解的奇异集和分支集。研究的一个重要部分是调查这些集合附近的解的渐近行为或这些集合本身的渐近行为。微分方程可以是椭圆型、双曲型或混合型的。有些问题与数学中的其他领域有着密切的联系，包括多复变函数和代数几何。PI将继续研究的另一类问题涉及方程中已知函数的水平集对解的存在性和性质的影响。当Gauss曲率的零点集良好时，二维黎曼流形在三维空间中的等距嵌入是一个特殊的问题，涉及奇异集的问题在材料科学和控制理论中经常出现。奇异集，顾名思义，就是那些出现奇异点的集合。确切的定义因问题的出现而异。通常不可能消除奇异集，即所谓的“坏集”。其中一个中心任务是确定条件下，可以控制的奇异集和条件下，奇异集是小的。在项目中提出的有关奇异集的问题是在其最简单的形式。它们与Erickson液晶模型和超导中的Ginzburg-Landau方程有关。PI认为，对这些数学问题的讨论将有助于科学家在各种应用中使用奇异集。

Nonlinear Partial Differential Equations and Applications Abstract of Proposed ResearchQing HanUnder this award, the principal investigator plans to continue his work in partial differential equations. In particular he will investigate the role of the nodal sets of solutions of differential equations, or more general level sets of functions. Also the singular sets and the branch sets of solutions. An important part of the study is the investigation of the asymptotic behavior of solutions near these sets or the asymptotic behavior of these sets themselves. The differential equations may be of elliptic, hyperbolic or mixed type. Some problems have close connections with other fields in mathematics, including several complex variables and algebraic geometry. Another class of problems that the PI would continue to work on involves the effect of level sets of known functions in the equations on the existence and properties of solutions. A particular problem is the isometric embedding of 2-dim Riemannian manifolds in 3-space when the zero set of Gauss curvature is well behaved.The problems involving singular sets occur in materials science and control theory. Singular sets, as the name suggests, are those sets where singularities occur. Precise definitions vary depending on the problems where they arise. It often is impossible to eliminate the singular sets, the so-called "bad sets". One of the central tasks is to identify the conditions under which the singular sets can be controlled and the conditions under which the singular sets are small. The proposed problems concerning singular sets in the project are in their simplest forms. They are related to the Erickson's model for liquid crystals and the Ginzburg-Landau equation in the superconductivity. The PI believes that the discussion of these mathematical problems will help scientists work with singular sets in various applications.