FAST：一种全异步自引力流体分裂时间积分器
FAST: A Fully Asynchronous Split Time-Integrator for Self-Gravitating Fluid
摘要：
本文提出了一种新的自引力流体系统积分的SPH算法。我们将自引力流体系统的哈密顿量分解为引力势和其他（动能和内能），并使用不同的时间步长进行积分。时间积分的方式类似于混合变量或多步长辛格式。我们进行了三次测试计算。一个是球形崩塌，一个是爆炸。我们还进行了一个现实的测试，其中初始模型是从合并星系的模拟。在所有的测试计算中，我们发现，当我们采用我们的积分方法时，引力相互作用的时间步数减少了近一个数量级。在实际测试的情况下，其中的暗物质潜力占主导地位的整个系统，总的计算时间显着减少。模拟结果与普通的个体时间步长法模拟结果基本一致。我们的新方法在不牺牲时间积分精度的情况下实现了良好的性能。
英文摘要：
We describe a new algorithm for the integration of self-gravitating fluid systems using SPH method. We split the Hamiltonian of a self-gravitating fluid system to the gravitational potential and others (kinetic and internal energies) and use different time-steps for their integrations. The time integration is done in the way similar to that used in the mixed variable or multiple stepsize symplectic schemes. We performed three test calculations. One was the spherical collapse and the other was an explosion. We also performed a realistic test, in which the initial model was taken from a simulation of merging galaxies. In all test calculations, we found that the number of time-steps for gravitational interaction were reduced by nearly an order of magnitude when we adopted our integration method. In the case of the realistic test, in which the dark matter potential dominates the total system, the total calculation time was significantly reduced. Simulation results were almost the same with those of simulations with the ordinary individual time-step method. Our new method achieves good performance without sacrificing the accuracy of the time integration.
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