标题： 在数值相对论中的柯西-特征提取 显示英文标题

标题： Cauchy-characteristic extraction in numerical relativity

摘要： 我们使用广义相对论的混合类时-类空初始值公式来计算引力辐射。 外部辐射解的确定基于类时世界管$\Gamma$上的边界值以及从$\Gamma$的初始横截面发出的外向类空锥上的特征数据。 我们介绍了用于在数值网格上演化这些初始数据的三维计算算法，该网格被紧化以将未来类空无限包含为有限网格点。 实现该算法的代码在准球对称区域进行了校准。 我们考虑将此过程应用于从内部柯西演化中提取无限远处的波形，这提供了$\Gamma$上的边界数据。 这是迈向柯西-特征匹配的第一步，在柯西-特征匹配中，边界$\Gamma$处的数据流是双向的，柯西和特征计算相互提供精确的边界值。 我们描述了实现匹配的策略，并表明对于小的目标误差，它比其他方法更计算高效。 显示英文摘要

摘要： We treat the calculation of gravitational radiation using the mixed timelike-null initial value formulation of general relativity. The determination of an exterior radiative solution is based on boundary values on a timelike worldtube $\Gamma$ and on characteristic data on an outgoing null cone emanating from an initial cross-section of $\Gamma$. We present the details of a 3-dimensional computational algorithm which evolves this initial data on a numerical grid, which is compactified to include future null infinity as finite grid points. A code implementing this algorithm is calibrated in the quasispherical regime. We consider the application of this procedure to the extraction of waveforms at infinity from an interior Cauchy evolution, which provides the boundary data on $\Gamma$. This is a first step towards Cauchy-characteristic matching in which the data flow at the boundary $\Gamma$ is two-way, with the Cauchy and characteristic computations providing exact boundary values for each other. We describe strategies for implementing matching and show that for small target error it is much more computationally efficient than alternative methods.