Dynamical Evolution of Globular Clusters

众所周知，由于两体引力相互作用，球状星团的核心向高密度状态演化。当地核的密度高于某一值时，我们必须考虑其他相互作用。我们称这一阶段的进化为后崩溃进化。对球状星团坍缩后演化的研究成为理论天体物理学中最重要的问题之一。在这个项目中，我们把恒星当作点质量，忽略了恒星有限大小的影响。在1985财年，我们用n体数值实验研究了球状星团核心的演化。当球状星团的核心密度变得足够高时，在核心内部就会形成硬双星。双星与野星相互作用，发生核心收缩的逆转。然而，当双星的结合能变得足够大时，双星会从核心中喷射出来，核心再次收缩。核心的密度再次变高，形成了硬双星。这导致了核心的再膨胀。因此，发现核心密度的振荡是由于硬双星的活动。1986财政年度，在剑桥大学天文研究所S.J. Aarseth博士的合作下，对n体编码进行了矢量化。结果，n体代码的计算速度提高了十倍以上。虽然加快了n体实验的速度，但仍然需要大量的计算时间。因此，要跟踪球状星团的长期演化是不可能的。我们试图通过建立简单的模型来跟踪球状星团核心的长期演化。我们已经知道了双星形成的概率，双星和野星之间相互作用的速率，以及能量产生的速率。我们正在利用这些数据制作球状星团核心的模型。目前调查还在进行中，还没有明确的结论。少

It is known that the cores of globular clusters evolve toward higher density states due to two-body gravitational interactions. When the densities of the cores become higher than a certain value, we have to take into account other interactions. We call the evolution of this stage post-collapse evolution. Investigations of post-collapse evolution of globular clusters become one of the most important problems in theoretical astrophysics.In this project we treated stars as point masses and neglected the effects of finite size of stars.In 1985 fiscal year we studied the evolution of cores of globular clusters with N-body numerical experiments. When the core densities of globular clusters become sufficiently high, hard binaries are formed inside the cores. The binaries interact with field stars and reversal of core contraction occurs. However, when the binding energies of the binaries become large enough, the binaries are ejected from the cores and the cores contract again. The densities of … More the cores become high again and hard binaries are formed. This leads to the reexpansion of the cores. Thus the oscillations of the core density were found to be due to the activity of hard binaries.In 1986 fiscal year N-body codes were vectorized with the collaboration of Dr. S.J. Aarseth, Institute of Astronomy, University of Cambridge. As the result, the computations with N-body code were speeded up more than ten times.Though N-body experiments are speeded up, a large amount of computational time is still necessary. Therefore it is impossible to follow the long-term evolution of globular clusters. We are attempting to follow the long-term evolution of cores of globular cluster by making simple models. We have known the probability of formation of binaries, the rate of interaction between binaries and field stars, and the rate of energy production. We are making models of cores of globular clusters with the use of these data. This investigation is under progress now and we have not got definite conclusions yet. Less