Seminar----Institute of Theoretical Physics，Chinese Academy of Sciences

Institute of Theoretical Physics
Chinese Academy of Sciences
Key Laboratory of Theoretical Physics
Seminar
Title 题目	Pre-inflationary universe in loop quantum cosmology
Speaker 报告人	Anzhong Wang
Affiliation 所在单位	Zhejiang University of Technology & Baylor University
Date 日期	2017-07-26 (Wednesday) 2：00 p.m.
Venue 地点	ITP New Building 6420
Abstract 摘要	Loop quantum cosmology (LQC) provides an elegant resolution of the big bang singularity by a quantum bounce in the deep Planck era. To study perturbations in such a framework two main approaches have been proposed, the deformed algebra and dressed metric approaches. With some reasonable assumptions, the deformed algebra approach is already ruled out by current observations. In this talk, I shall first give a brief review on LQC and explain the reasons why the deformed algebra approach is inconsistent with observations. Then, I shall present our recent results on the investigations of the dressed metric approach. In particular, I shall show that, when the kinetic energy of the inflaton dominates at the quantum bounce, the evolutions of the flat FLRW background and its linear (scalar and tensor) perturbations are always universally divided into three different phases before reheating: bouncing, transition and slow-roll inflation. The evolutions are universal and independent of the inflationary potentials during the bouncing and transition phases and can be given analytically. We calculate the corresponding Bogoliubov coefficients at the onset of the slow-roll inflation, which are valid for any inflationary models with a single scalar field, and show that particles are generically created during the pre-inflationary period. Matching them to those in the slow-roll inflationary phase, we investigate the effects of the quantum bounce on the power spectra and find features that can be tested by current and forthcoming observations. In particular, to be consistent with the Planck 2015 data, the universe must have expanded at least 132 e-folds since the bounce.
Contact person 所内联系人	Rong-Gen Cai