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arXiv 1503.06225math.DG
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关于$\mathbb{R}^{2,2}$中的Lorentz曲面

On Lorentzian surfaces in $\mathbb{R}^{2,2}$

Pierre Bayard, Victor Patty, Federico Sánchez-Bringas

摘要:

研究了$\mathbb{R}^{2,2},$中Lorentz曲面的二阶不变量及其第二基本型的曲率双曲线。除了四个自然不变量外,在某些退化情况下还出现了新的不变量。然后引入洛伦兹曲面的高斯映射,给出紧致洛伦兹曲面的全高斯曲率和法曲率为零的外在证明。利用高斯映射和二阶不变量研究了洛伦兹曲面的渐近方向,并讨论了它们的因果性质。我们还考虑了渐近线与平均方向曲线的关系。最后,我们引入并描述了拟脐曲面,以及四个经典不变量为零的曲面。

英文摘要:

We study the second order invariants of a Lorentzian surface in $\mathbb{R}^{2,2},$ and the curvature hyperbolas associated to its second fundamental form. Besides the four natural invariants, new invariants appear in some degenerate situations. We then introduce the Gauss map of a Lorentzian surface and give an extrinsic proof of the vanishing of the total Gauss and normal curvatures of a compact Lorentzian surface. The Gauss map and the second order invariants are then used to study the asymptotic directions of a Lorentzian surface and discuss their causal character. We also consider the relation of the asymptotic lines with the mean directionally curved lines. We finally introduce and describe the quasi-umbilic surfaces, and the surfaces whose four classical invariants vanish identically.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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