A popular approach in numerical simulations of black hole binaries is to model black holes as punctures in the fabric of spacetime. The location and the properties of the black hole punctures are tracked with apparent horizons, namely outermost marginally outer trapped surfaces (MOTSs). As the holes approach each other, a common apparent horizon suddenly appears, engulfing the two black holes and signaling the merger. The evolution of common apparent horizons and their connection with gravitational wave emission have been studied in detail with the framework of dynamical horizons. We present a study of the dynamics of the MOTSs and their punctures in the interior of the final black hole. The study focuses on head-on mergers for various initial separations and mass ratios. We find that MOTSs intersect for most of the parameter space. We show that for those situations in which they do not, it is because of the singularity avoidance property of the moving puncture gauge condition used in the study. Although we are unable to carry out evolutions that last long enough to show the ultimate fate of the punctures, our results suggest that MOTSs always intersect and that at late times their overlap is only partial. As a consequence, the punctures inside the MOTSs, although close enough to each other to act effectively as a single puncture, do not merge.

中文翻译：

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在最终黑洞内部：穿刺和被困表面动力学

黑洞双星数值模拟的一种流行方法是将黑洞建模为时空结构中的穿孔。黑洞穿孔的位置和属性是用明显的视界来追踪的，即最外边缘的被困表面（MOTS）。当两个黑洞相互靠近时，一个共同的视界突然出现，吞没了两个黑洞并发出合并信号。以动力视界为框架，详细研究了常见视视界的演化及其与引力波发射的关系。我们对 MOTS 的动力学及其在最终黑洞内部的穿刺进行了研究。该研究侧重于各种初始分离和质量比的正面合并。我们发现 MOTS 与大部分参数空间相交。我们表明，对于那些不这样做的情况，这是因为研究中使用的移动穿刺规条件的奇异性避免特性。尽管我们无法进行持续足够长的进化以显示穿刺的最终命运，但我们的结果表明 MOTS 总是相交，并且在后期它们的重叠只是部分的。因此，MOTS 内的穿孔虽然彼此足够接近以有效地充当单个穿孔，但不会合并。我们的结果表明 MOTS 总是相交，并且在后期它们的重叠只是部分的。因此，MOTS 内的穿孔虽然彼此足够接近以有效地充当单个穿孔，但不会合并。我们的结果表明 MOTS 总是相交，并且在后期它们的重叠只是部分的。因此，MOTS 内的穿孔虽然彼此足够接近以有效地充当单个穿孔，但不会合并。