Given a two-dimensional mapping U whose components solve a divergence structure elliptic equation, we give necessary and sufficient conditions on the boundary so that U is a global diffeomorphism.

中文翻译：

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全局微分同构 $$\sigma$$ σ -谐波映射

给定一个二维映射U，其分量求解一个发散结构椭圆方程，我们给出边界上的充分必要条件，使得U是一个全局微分同胚。