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arXiv 0911.0973gr-qc
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用伪谱方法研究BSSN系统的黑洞长期演化

Long term black hole evolution with the BSSN system by pseudospectral methods

Wolfgang Tichy

摘要:

利用BSSN系统,利用伪谱方法研究了质量为$M$的单个黑洞的长期演化。对于我们的模拟,我们使用SGRID代码,其中BSSN系统以其标准的二阶空间形式实现。以前我们发现这样的模拟是相当不稳定的。本文的主要目标是提出两个改进,现在允许我们进化更长的时间。第一个改进与切除的黑洞内部的边界条件有关。我们现在使用一个规范条件,确保所有的模式都进入黑洞,这样在切除表面就不需要边界条件了。第二个更重要的改进与我们特定的数值方法有关,并且涉及基于将用于角度依赖性的双傅立叶展开投影到球谐函数上的滤波器。有了这两个改进,现在可以很容易地进化到几千个$M$。唯一剩下的限制似乎是这里使用的辐射外边界条件。然而,这个问题可以通过将外边界的位置向外推来改善,这会导致更长的运行时间。

英文摘要:

We present long term evolutions of a single black hole of mass $M$ with the BSSN system using pseudospectral methods. For our simulations we use the SGRID code where the BSSN system is implemented in its standard second order in space form. Previously we found that such simulations are quite unstable. The main goal of this paper is to present two improvements which now allow us to evolve for longer times. The first improvement is related to the boundary conditions at the excised black hole interior. We now use a gauge condition that ensures that all modes are going into the black hole, so that no boundary conditions are needed at the excision surface. The second more significant improvement has to do with our particular numerical method and involves filters based on projecting the double Fourier expansions used for the angular dependence onto Spherical Harmonics. With these two improvements it is now easily possible to evolve for several thousand $M$. The only remaining limitation seems to be the radiative outer boundary conditions used here. Yet this problem can be ameliorated by pushing out the location of the outer boundary, which leads to even longer run-times.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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