Can the Scale Factor be Rippled?

Abstract

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 the scale factor against a slowly evolving background, which is not affected by such 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 nonlinear oscillations. As is shown these nonlinear oscillations can be treated as a nonlinear gauge wave.