当自转参数（spin parameter）a（常称作 特定角动量 （ specific angular momentum） ）其值为零，则无旋转，度规退化成 史瓦西度规。a=M的例子对应到最大旋转程度的质量物体。
双语例句
1
For a stationary, adiabatic flow the specific energy E, specificangularmomentum L and mass accretion rate M are constant in space.
对于静态、绝热吸积流，比能量E、比角动量L和质量吸积率M都是空间的常量。
2
This paper analyzes and discusses specific application of the conservation law of angularmomentum in competitive sports, such as aerial tumbling, trunk rotation and somersault.