论文标题
引入了一种新的多粒子碰撞方法，用于致密恒星系统的演变。碰撞测试N体模拟
Introducing a new multi-particle collision method for the evolution of dense stellar systems. Crash-test N-body simulations
论文作者
论文摘要
恒星系统大致分为碰撞和非碰撞。后者是具有较长松弛时间尺度的大N系统，可以模拟无视两体相互作用，而计算昂贵的直接N体模拟或近似方案都需要正确地对前者进行建模。大型球状群集和核星簇，带有哈勃时间的放松时间尺度，足够小，足以显示出一些碰撞行为，并且足够大，无法使用直接的$ n $体制代码和当前的硬件进行模拟。我们介绍了一种新方法来模拟碰撞恒星系统，并通过与小型$ n $仿真的直接$ n $ body代码进行验证。密集恒星系统代码（MPCDSS）的多粒子碰撞是使用多粒子碰撞方法不断发展的恒星系统的新代码。这种方法相当于随机碰撞规则，该规则允许在经历碰撞的颗粒群体上精确保存能量和动量。代码复杂性在粒子数中用$ n \ log n $缩放。与蒙特卡罗代码不同，MPCDS可以很容易地对不对称，非均匀，不删除和旋转系统进行建模，同时使我们能够遵循单个恒星的轨道。我们将带有MPCDSS和直接夏季代码NBODY6的小型（$ n = 3.2 \ times 10^4 $）星形簇进化，发现了关键指示器的类似演变。然后，我们在$ 10^4-10^6 $星范围内模拟不同的初始条件。 MPCDSS弥合了可以使用直接$ n $体制代码和大型非碰撞系统模拟的小型碰撞系统之间的差距。 MPCDS在原则上使我们能够模拟球状簇，例如欧米茄CEN和M54，甚至是核星簇，超出了当前直接N体代码的限制，就粒子的数量而言。
Stellar systems are broadly divided into collisional and non-collisional. The latter are large-N systems with long relaxation timescales and can be simulated disregarding two-body interactions, while either computationally expensive direct N-body simulations or approximate schemes are required to properly model the former. Large globular clusters and nuclear star clusters, with relaxation timescales of the order of a Hubble time, are small enough to display some collisional behaviour and big enough to be impossible to simulate with direct $N$-body codes and current hardware. We introduce a new method to simulate collisional stellar systems, and validate it by comparison with direct $N$-body codes on small-$N$ simulations. The Multi-Particle collision for Dense stellar systems Code (MPCDSS) is a new code for evolving stellar systems with the Multi-Particle Collision method. Such method amounts to a stochastic collision rule that allows to conserve exactly the energy and momentum over a cluster of particles experiencing the collision. The code complexity scales with $N \log N$ in the number of particles. Unlike Monte-Carlo codes, MPCDSS can easily model asymmetric, non-homogeneous, unrelaxed and rotating systems, while allowing us to follow the orbits of individual stars. We evolve small ($N = 3.2 \times 10^4$) star clusters with MPCDSS and with the direct-summation code NBODY6, finding a similar evolution of key indicators. We then simulate different initial conditions in the $10^4 - 10^6$ star range. MPCDSS bridges the gap between small, collisional systems that can be simulated with direct $N$-body codes and large noncollisional systems. MPCDSS in principle allows us to simulate globular clusters such as Omega Cen and M54 and even the nuclear star cluster, beyond the limits of current direct N-body codes in terms of the number of particles.
