标题： 测试Ω_0=1宇宙中的最小作用量原理 显示英文标题

标题： Testing the Least Action Principle in an Omega_0=1 Universe

摘要： 最小作用量原理（LAP）是一种动态严格的推导星系轨道历史的方法。 尤其它是一种对 Ω_0 的检验，预测当前时期星系速度作为位置和宇宙背景函数。 它最适用于正在坠落的结构，如本星系群，在这种应用中表明首选的宇宙模型是 Ω_0 = 0.1 和 h = 0.75（h 是哈勃参数，单位为 100 公里每秒每兆秒差距）。 该方法假设所有质量都像可见星系一样分布。 我们测试了LAP方法在从Ω_0=1 N体模拟中提取的类似本星系群系统中的可靠性。 虽然星系的轨道被定性地很好地重建，但LAP系统性地低估了系统的质量。 这一失败归因于存在围绕可见星系弱聚类的扩展晕，这阻止了大量群质量被LAP技术检测到。 我们得出结论，LAP方法不能排除在本星系群尺度上 Ω_0=1 的值。 通过将此技术应用于正在坠落的系统，如包含分离距离远大于星系大小的物体的星团，可以更好地限制 Ω_0 的值。 显示英文摘要

摘要： The least action principle (LAP) is a dynamically rigorous method for deriving the history of galaxy orbits. In particular it is an Omega_0 test, predicting current epoch galaxy velocities as a function of position and of the cosmological background. It is most usefully applied to in--falling structures, such as the local group, where its application indicates that the preferred cosmological model is Omega_0 = 0.1 and h=0.75 (h is the Hubble parameter in units of 100 Km s^-1 Mpc^-1). The method assumes that all the mass acts as if it were distributed as the visible galaxies. We test the reliability of the LAP to Local Group-like systems extracted from Omega_0=1 N--body simulations. While the orbits of the galaxies are qualitatively well reconstructed, the LAP systematically underestimates the mass of the system. This failure is attributed to the presence of extended halos weakly clustered around visible galaxies which prevent a large fraction of the group mass from being detected by the LAP technique. We conclude that the LAP method cannot rule out an Omega_0=1 value on the Local Group scale. Better constraints on Omega_0 may be obtained by applying this technique to in--falling systems, such as clusters, containing objects with separations large compared to galaxy sizes.