Beran Tobias, Sämann Clemens
Faculty of Mathematics University of Vienna Vienna Austria.
J Lond Math Soc. 2023 May;107(5):1823-1880. doi: 10.1112/jlms.12726. Epub 2023 Feb 20.
Within the synthetic-geometric framework of Lorentzian (pre-)length spaces developed in Kunzinger and Sämann (Ann. Glob. Anal. Geom. (2018), no. 3, 399-447) we introduce a notion of a hyperbolic angle, an angle between timelike curves and related concepts such as timelike tangent cone and exponential map. This provides valuable technical tools for the further development of the theory and paves the way for the main result of the article, which is the characterization of timelike curvature bounds (defined via triangle comparison) with an angle monotonicity condition. Further, we improve on a geodesic non-branching result for spaces with timelike curvature bounded below.
在Kunzinger和Sämann(《Ann. Glob. Anal. Geom.》(2018年),第3期,399 - 447页)所发展的洛伦兹(预)长度空间的综合几何框架内,我们引入了双曲角的概念、类时曲线之间的夹角以及诸如类时切锥和指数映射等相关概念。这为该理论的进一步发展提供了有价值的技术工具,并为本文的主要结果铺平了道路,该结果是用一个角度单调性条件来刻画类时曲率界(通过三角形比较定义)。此外,我们改进了类时曲率有下界的空间的测地线非分支结果。