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On the minimal accuracy required for simulating self-gravitating systems by means of direct N-body methods

机译:关于模拟自引力系统所需的最小精度   通过直接的N体方法

摘要

The conservation of energy, linear momentum and angular momentum areimportant drivers for our physical understanding of the evolution of theUniverse. These quantities are also conserved in Newton's laws of motion undergravity \citep{Newton:1687}. Numerical integration of the associated equationsof motion is extremely challenging, in particular due to the steady growth ofnumerical errors (by round-off and discrete time-stepping,\cite{1981PAZh....7..752B,1993ApJ...415..715G,1993ApJ...402L..85H,1994LNP...430..131M})and the exponential divergence \citep{1964ApJ...140..250M,2009MNRAS.392.1051U}between two nearby solution. As a result, numerical solutions to the generalN-body problem are intrinsically questionable\citep{2003gmbp.book.....H,1994JAM....61..226L}. Using brute force integrationsto arbitrary numerical precision we demonstrate empirically that ensembles ofdifferent realizations of resonant 3-body interactions produce statisticallyindistinguishable results. Although individual solutions using commonintegration methods are notoriously unreliable, we conjecture that an ensembleof approximate 3-body solutions accurately represents an ensemble of truesolutions, so long as the energy during integration is conserved to better than1/10. We therefore provide an independent confirmation that previous work onself-gravitating systems can actually be trusted, irrespective of the intrinsicchaotic nature of the N-body problem.
机译:能量守恒,线性动量和角动量是我们对宇宙演化的物理理解的重要驱动力。牛顿的运动重力定律\ citep {Newton:1687}中也保留了这些量。相关运动方程的数值积分非常具有挑战性,特别是由于数值误差的稳定增长(通过四舍五入和离散时间步长,引用{1981PAZh .... 7..752B,1993ApJ ... 415。 .715G,1993ApJ ... 402L..85H,1994LNP ... 430..131M})和两个附近解之间的指数散度\ citep {1964ApJ ... 140..250M,2009MNRAS.392.1051U}。结果,一般N体问题的数值解本质上是有问题的\ citep {2003gmbp.book ..... H,1994JAM .... 61..226L}。使用蛮力积分到任意数值精度,我们从经验上证明,共振3体相互作用的不同实现的集合产生统计上难以区分的结果。尽管众所周知,使用普通积分方法的单个解决方案并不可靠,但我们可以推测,只要将积分过程中的能量守恒于1/10以上,则近似三体解决方案的集合就可以准确地表示真实解决方案的集合。因此,我们提供了一个独立的确认,即无论N体问题的内在混沌性质如何,以前对自重系统所做的工作实际上都是可以信任的。

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