题目：Fenchel Theorem, Tangent Indicatrix and Alternative Theorem in the Lorentz Space

时间：2016年7月25日（周一）下午15:00-16:00

报 告 人：马翔教授(北京大学)

地点：致远楼107室

报告摘要： In this talk I will introduce our recent work on a generalization of the Fenchel theorem to the 3-dimensional Lorentz space. The total curvature of a spacelike closed curve is the same as the length of its tangent indicatrix. The estimation of this length is non-trivial. Here we will explain our discovery of an alternative phenomenon about closed spacelike curves on the de-sitter space, which helps to establish the desired inequality. Moreover, this also helps to obtain a necessary and sufficient condition for a curve to be realizable as the tangent indicatrix.