Low Energy Behavior of a Quantized Scalar Field in the Linearly Expanding Universe

摘要

We study positive frequency mode solutions of a massive scalar field at an initial stage in the spatially flat, linearly expanding Robertson-Walker universe. The essential point is that the initial time is taken to be small enough, but non-zero (e.g., the Planck time), and the mode is determined by a kind of the WKB conditions. We calculate the created particle spectrum, and show that its low energy behavior is considerably different from the previous results. (Atomindex citation 14:721224)