标题： 尺度因子可以波动吗？ 显示英文标题

标题： Can the scale factor be rippled?

摘要： 我们提出一个问题：宇宙学尺度因子是否为局部振荡量？ 这个问题在两个经典的1+1维模型框架下进行研究：第一个模型是处于弯曲背景下的弦，第二个模型是非均匀的Bianchi I模型。 对于弦模型，证明存在一种规范和初始条件，使得尺度因子在缓慢演化的背景下发生振荡，这种振荡“在平均意义上”不会影响该背景。 对于具有共形时间规范的非均匀Bianchi I模型，初始均匀的尺度因子可以变得非均匀并经历非线性振荡。 如所示，这些非线性振荡可被视为非线性规范波。 显示英文摘要

摘要： We address an issue: would the cosmological scale factor be a locally oscillating quantity? This problem is examined in the framework of two classical 1+1-dimensional models: the first one is a string against a curved background, and the second one is an inhomogeneous Bianchi I model. For the string model, it is shown that there exist the gauge and the initial condition providing an oscillation of scale factor against a slowly evolving background, which is not affected by such an oscillation "at the mean". For the inhomogeneous Bianchi I model with the conformal time gauge, an initially homogeneous scale factor can become inhomogeneous and undergo the nonlinear oscillations. As is shown these nonlinear oscillations can be treated as a nonlinear gauge wave.