时空中的Minkowski公式和Alexandrov定理
Minkowski formulae and Alexandrov theorems in spacetime
摘要：
从共形Killing-Yano两形式出发，将经典的Minkowski公式推广到时空中的余维为2的类空子流形。作为应用，我们得到了静态球对称时空中类空余维2子流形的一个Alexandrov型定理：具有常归一化零展开（零中曲率）的余维2子流形必位于无切变（脐）零超曲面中.这些结果推广到高阶曲率不变量。特别地，引入了混合高阶中曲率的概念，突出了子流形的特殊零几何。最后，对具有常混合高阶中曲率的类空子流形建立了Alexandrov型定理，这些子流形是欧几里得空间中具有常Weingarten曲率的超曲面的推广.
英文摘要：
The classical Minkowski formula is extended to spacelike codimension-two submanifolds in spacetimes which admit "hidden symmetry" from conformal Killing-Yano two-forms. As an application, we obtain an Alexandrov type theorem for spacelike codimension-two submanifolds in a static spherically symmetric spacetime: a codimension-two submanifold with constant normalized null expansion (null mean curvature) must lie in a shear-free (umbilical) null hypersurface. These results are generalized for higher order curvature invariants. In particular, the notion of mixed higher order mean curvature is introduced to highlight the special null geometry of the submanifold. Finally, Alexandrov type theorems are established for spacelike submanifolds with constant mixed higher order mean curvature, which are generalizations of hypersurfaces of constant Weingarten curvature in the Euclidean space.
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