Abstract
We study a nonsingular bounce inflation model, which can drive the early universe from a contracting phase, bounce into an ordinary inflationary phase, followed by the reheating process. Besides the bounce that avoided the Big-Bang singularity which appears in the standard cosmological scenario, we make use of the Horndesky theory and design the kinetic and potential forms of the lagrangian, so that neither of the two big problems in bouncing cosmology, namely the ghost and the anisotropy problems, will appear. The cosmological perturbations can be generated either in the contracting phase or in the inflationary phase, where in the latter the power spectrum will be scale-invariant and fit the observational data, while in the former the perturbations will have nontrivial features that will be tested by the large scale structure experiments. We also fit our model to the CMB TT power spectrum.
Highlights
In bouncing inflation scenario there will be two more latent problems
We study a nonsingular bounce inflation model, which can drive the early universe from a contracting phase, bounce into an ordinary inflationary phase, followed by the reheating process
The phenomenology of bounce inflation scenario was first studied in [41,42,43], where it was shown that such a scenario can obtain scale-invariant scalar perturbations that can fit with the data, the perturbations generated before the bounce can give rise to tilted spectrum, which can explain the suppression of CMB TT spectrum at large scales
Summary
As has been demonstrated in the introduction, in order to avoid ghost instability, it is useful to make use of Galileon theory to build up the bounce inflation model. An anisotropy-free contraction phase which requires the EoS larger than unity generally leads to a negative potential, the simplest Lagrangian of which is: Lcon = X − V con(φ) ,. We will choose functions k(φ), t(φ), G(X, φ) and V (φ) so that they can approach Lagrangians (2.4) and (2.5) in the limits of past and future, respectively. For the solution where φ increases monotonically (which is a very natural solution), one will get the anisotropy-free contraction in the past and inflation in the future, between which the bounce is triggered around φ = 0. Using tanh-like shape function, we can naturally connect V con(φ) and V inf (φ) so that the field φ can evolve naturally from a lower potential to a higher one, leading to inflation. The whole evolution of the φ, φ, H and w are sketched in figure 3
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