标题： 准局域引力能量和角动量的最优参考选择 显示英文标题

标题： An Optimal Choice of Reference for the Quasi-Local Gravitational Energy and Angular Momentum

摘要： 只要能够提供适当的演化矢量场和合适的参考几何，引力哈密顿量的边界项就可以用来给出准局域量的值。在区域的双曲面边界上，我们建议使用动态时空与参考几何之间的{\em 四维等距匹配}以及能量极值来找到最佳的参考匹配和适当的准 Killing 矢量。在这里我们考虑轴对称时空的情形。特别是对于克尔度规，我们可以显式求解方程以找到最佳匹配的参考和准 Killing 矢量。这导致了准局域边界项的确切表达式以及我们最优准局域能量和角动量的值。 显示英文摘要

摘要： The boundary term of the gravitational Hamiltonian can be used to give the values of the quasi-local quantities as long as one can provide a suitable evolution vector field and an appropriate reference. On the two-surface boundary of a region we have proposed using {\em four dimensional isometric matching} between the dynamic spacetime and the reference geometry along with energy extremization to find both the optimal reference matching and the appropriate quasi-Killing vectors. Here we consider the axisymmetric spacetime case. For the Kerr metric in particular we can explicitly solve the equations to find the best matched reference and quasi-Killing vectors. This leads to the exact expression for the quasi-local boundary term and the values of our optimal quasi-local energy and angular momentum.