Evolution of cosmological perturbations in the long wavelength limit
Evolution of cosmological perturbations in the long wavelength limit
复制标题
长波长极限下宇宙扰动的演化
DOI：
10.1103/physrevd.57.7177
复制
发表时间：
1997
影响因子：
5
通讯作者：
Takashi Hamazaki
中科院分区：
文献类型：
--
作者：
Hideo Kodama;Takashi Hamazaki
对于空间平坦宇宙模型上的标量扰动，研究了宇宙学扰动方程组解的长波极限与精确齐次背景方程组解的扰动之间的关系。结果表明，如果物质只由标量场组成，则齐次微扰仅满足与动量约束相对应的附加条件时，齐次微扰才与某些非齐次微扰的长波极限一致。相反，如果描述物质的基本变量包含矢量场，则不会出现这种约束，就像流体的情况一样。此外，作为一般分析的副产品，证明了长波极限下微扰方程存在两个普适精确解，它们仅用背景量表示。它们代表绝热增长模和绝热衰减模，对应于众所周知的理想流体系统和标量场系统的精确解。
The relation between the long wavelength limit of solutions to the cosmological perturbation equations and the perturbations of solutions to the exactly homogeneous background equations is investigated for scalar perturbations on spatially flat cosmological models. It is shown that a homogeneous perturbation coincides with the long wavelength limit of some inhomogeneous perturbation only when the former satisfies an additional condition corresponding to the momentum constraint if the matter consists only of scalar fields. In contrast, no such constraint appears if the fundamental variables describing the matter contain a vector field as in the case of a fluid. Further, as a byproduct of this general analysis, it is shown that there exist two universal exact solutions to the perturbation equations in the long wavelength limit, which are expressed only in terms of the background quantities. They represent adiabatic growing and decaying modes, and correspond to the well-known exact solutions for perfect fluid systems and scalar field systems.