标题： 共振线在膨胀宇宙中的时间演化 显示英文标题

标题： The Time Development of a Resonance Line in the Expanding Universe

摘要： 研究了均匀膨胀介质中共振线的时间依赖光谱轮廓，通过数值求解改进的福克-普朗克扩散方程。 这些解用于确定接近线中心时达到准静态解所需的时间。 推导出一个简单的弛豫时间缩放律，并将其拟合到数值结果上。 结果应用于氢的原初复合期间的莱曼阿尔法散射情况。 对于广泛的宇宙学模型，发现弛豫时间小于复合时间尺度，尽管差距不大。 因此，在宇宙学复合计算中的准静态解的标准假设是合理的，不应在解中引起实质性误差。 显示英文摘要

摘要： The time-dependent spectral profile of a resonance line in a homogeneous expanding medium is studied by numerically solving an improved Fokker-Planck diffusion equation. The solutions are used to determine the time required to reach a quasi-static solution near the line center. A simple scaling law for this relaxation time is derived and is fitted to the numerical results. The results are applied to the case of Lyman alpha scattering during primordial recombination of hydrogen. For a wide range of cosmological models it is found that the relaxation times are smaller than the recombination timescale, although not by a very large factor. Thus the standard assumption of a quasi-static solution in cosmological recombination calculations is reasonably valid, and should not cause substantial errors in the solutions.