Eur. Phys. J. C (2013) 73: 2341
https://doi.org/10.1140/epjc/s10052-013-2341-x

Regular Article - Theoretical Physics

Perturbations in symmetric Lee–Wick bouncing universe

¹ Institute of Convergence Fundamental Studies & School of Liberal Arts, Seoul National University of Science and Technology, Seoul, 139-743, Korea
² Department of Physics, BK21 Physics Research Division, Institute of Basic Science, Sungkyunkwan University, Suwon, 440-746, Korea
³ Institute for the Early Universe, Ewha Womans University, Seoul, 120-750, Korea

^* e-mail: okab@skku.edu

Received: 8 February 2013
Published online: 7 March 2013

Abstract

We investigate the tensor and the scalar perturbations in the symmetric bouncing universe driven by one ordinary field and its Lee–Wick partner field which is a ghost. We obtain the even- and the odd-mode functions of the tensor perturbation in the matter-dominated regime. The tensor perturbation grows in time during the contracting phase of the universe, and decays during the expanding phase. The power spectrum for the tensor perturbation is evaluated and the spectral index is given by n _T=6. We add the analysis on the scalar perturbation by inspecting the even- and the odd-mode functions in the matter-dominated regime, which was studied numerically in our previous work. We conclude that the comoving curvature by the scalar perturbation is constant in the super-horizon scale and starts to decay in the far sub-horizon scale while the universe expands.