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arXiv 1105.6347gr-qchep-th
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寻找一般稳态真空黑洞的数值方法

A numerical approach to finding general stationary vacuum black holes

Alexander Adam, Sam Kitchen, Toby Wiseman

摘要:

谐波爱因斯坦方程是真空爱因斯坦方程的补充规范固定项,我们采取的是德图尔克。对于静态黑洞解析延拓到视界无边界的黎曼流形,这个方程以前已被证明是椭圆的,而Ricci流和Newton方法提供了很好的数值算法来求解它,这里我们将这些技术推广到任意的同时齐性情形,这种情形必须用Lorentz签名来处理。对于具有整体类时Killing向量的定常时空,调和爱因斯坦方程是椭圆的。在视界和能区的存在下,情况就不那么明显了。受刚性定理的启发,我们研究了一类静止的黑洞时空,这类时空以前由Harmark考虑过,一般足以包括高维中的渐近平坦情形。我们认为谐波爱因斯坦方程一贯截断这类时空给出一个椭圆问题。Killing视界和旋转对称轴是这个问题的边界,我们确定边界条件。作为一个简单的例子,我们数值构造四维旋转黑洞在一个腔使用安德森的边界条件。我们证明了牛顿的方法和里奇流找到这些洛伦兹的解决方案。

英文摘要:

The Harmonic Einstein equation is the vacuum Einstein equation supplemented by a gauge fixing term which we take to be that of DeTurck. For static black holes analytically continued to Riemannian manifolds without boundary at the horizon this equation has previously been shown to be elliptic, and Ricci flow and Newton's method provide good numerical algorithms to solve it. Here we extend these techniques to the arbitrary cohomogeneity stationary case which must be treated in Lorentzian signature. For stationary spacetimes with globally timelike Killing vector the Harmonic Einstein equation is elliptic. In the presence of horizons and ergo-regions it is less obviously so. Motivated by the Rigidity theorem we study a class of stationary black hole spacetimes, considered previously by Harmark, general enough to include the asymptotically flat case in higher dimensions. We argue the Harmonic Einstein equation consistently truncates to this class of spacetimes giving an elliptic problem. The Killing horizons and axes of rotational symmetry are boundaries for this problem and we determine boundary conditions there. As a simple example we numerically construct 4D rotating black holes in a cavity using Anderson's boundary conditions. We demonstrate both Newton's method and Ricci flow to find these Lorentzian solutions.

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