宇宙大尺度结构数值模拟的研究进展

The Frontier of Studies on Cosmological Structure Numerical Simulation

宇宙的结构是由初始密度扰动发展而成的。在引力和宇宙膨胀的作用下,初始密度扰动不断增长,经过线性和非线性阶段,逐渐演化为现今的宇宙结构。在一个给定的宇宙学模型下,可以用一系列动力学方程来描述宇宙中暗物质和重子物质的运动及演化历史。在过去的几十年间,随着算法的完善和计算机技术的发展,从最初几十个粒子的纯引力模拟到1010个粒子在秒差距量级的多体加流体动力学模拟,大量不同的数值模拟技术被用来研究宇宙结构的形成和演化。在这个过程中,数值模拟的分辨率和精度不断提高,模型中对重子物质物理过程的描述也越来越完善。这些模拟技术与观测结果相结合,使人们对宇宙的大尺度结构以及星系团的形成和演化有了更深刻的理解,也在一定程度上影响了观测的发展方向和设备研发。不同数值模拟结果在纯引力研究方面得到了较好的统一,但不同的星系模型使得流体模拟的结果存在较大的差异。

The cosmic structure formation and evolution is driven by the gravitational action combined with the primordial density perturbation and multiple physical processes. With theinteraction between gravity and cosmic expansion, the primordial density perturbation continuously increased, and evolved into the current cosmic structure by linear and nonlinear evolution. Given a cosmological model, the history of dark matter and baryonic matter can be traced by a series of idealized dynamical equations. In the past several decades, there have been a great deal of numerical techniques to study the cosmic formation and evolution, from original pure gravitational numerical simulations with dozens of particles to modern hydrodynamical simulations with 1010 particles and pc-scale resolution region. This development is contributed by the perfection of numerical algorithms and progress of computational techniques, causing the resolution and accuracy of simulation much higher. With the benefit from a large amount of galaxy surveys, astronomers have a deeper understanding for the physical processes affecting galaxy formation, which improves the sub-grid physical processes description in algorithms. Combined these simulation results with that of observations, people have a more profound understanding for large scale structure of the universe, formation and evolution of the galaxy clusters. Those results also affect the development direction of observation and equipment research. The comparisons between different simulation codes confirm that results from the pure gravitational simulations are similar, but different hydro-dynamical simulations show much inconsistent conclusions, because of difference of the galaxy formation model. The history of large scale cosmological numerical simulation and a large kind of modern numerical simulations are reviewed in this paper.