Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
; Chinese Acad Sci, Interdisciplinary Ctr Theoret Studies, Beijing 100080, Peoples R China
; CCAST, World Lab, Beijing 100080, Peoples R China
; Chinese Acad Sci, Inst Theoret Phys, Beijing 100080, Peoples R China
In this paper we describe the evolution of various expanding and contracting phases before the "bounce" in Einstein frame. Focusing on the case of a single scalar field, in terms of the parameter w of the state equation, four different regions denoting different expanding and contracting phases are pointed out. We discuss possible scenarios generating the nearly scale-invariant spectrum and show that the inflation and other alternative scenarios recently proposed can be placed in different positions of these regions. Our work offers an interesting classification for the primordial perturbation spectra from various phases before the "bounce," which may have important implications for building an early universe scenario embedded in possible high-energy theories.