Abstract
We investigate the post-bounce background dynamics in a certain class of single bounce scenarios studied in the literature, in which the cosmic bounce is driven by a scalar field with negative exponential potential such as the ekpyrotic potential. We show that those models can actually lead to cyclic evolutions with repeated bounces. These cyclic evolutions, however, do not account for the currently observed late-time accelerated expansion and hence are not cosmologically viable. In this respect we consider a new kind of cyclic model proposed recently and derive some cosmological constraints on this model.
Highlights
We investigate the post-bounce background dynamics in a certain class of single bounce scenarios studied in the literature, in which the cosmic bounce is driven by a scalar field with negative exponential potential such as the ekpyrotic potential
In this paper we have studied the post-bounce background dynamics in bouncing models, in which the cosmic bounce is driven by a scalar field φ with negative exponential potential such as the ekpyrotic potential [10,11,12,13,14,15,16]
We have shown that the scalar plays an important role even during matter/radiation dominated expanding phase, due to the nontrivial dynamics of the scalar field with negative exponential potential, and that the post-bounce expanding universe dominated by matter/radiation does not correspond to that of the standard big bang cosmology
Summary
We investigate the post-bounce dynamics of the background including φ, in the presence of a regular matter/radiation fluid, which we represent with energy density. As stated in the Introduction, the bounce phase is followed by the kinetic expanding phase, in which the kinetic energy density of φ dominates over the potential of φ and ρm, 4Without loss of generality, the bounce can be set to take place around φ = 0. We emphasize that the expressions (2.11)–(2.14) are valid during the kinetic phase (dominated by the kinetic energy density of φ) as well as radiation/matter dominated phase, as far as the potential term can be neglected. We work out in detail the time evolution of φ during the radiation/matter domination phase. During this phase ρm and H evolve as ρm 3(1 + wm) (t + c)2 , 3(1 + wm) t + c (2.17). This picture will be confirmed by numerical analysis given
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