| Popis: |
A single field matter bounce with an exponential potential is numerically studied. The quantum bounce prescribed when the kinetic term dominates the evolution of the background were already demonstrated in the literature. To form a com- plete background, the quantum bounce is matched with the classical exponential- potential-driven evolution, which presents a past matter attractor. This configu- ration allows two possible mutually excluding scenarios: case A, in which a Dark Energy (DE) epoch is present in the contraction phase and case B, in which DE is present in the expansion phase. The latter is used as the background to study the cosmological perturbations. The evolution of the primordial scalar and tensor modes from vacuum initial condi- tions shows a consistent power spectra with the right amplitudes, tensor-to-scalar ratio and spectral index. Since bounce cosmologies suffers from the growth of anisotropy during contrac- tion phase, a matter bounce driven by a Galileon scalar field with an ekpyrotic potential is studied. Previous studies with this model claims that the final back- ground dynamics suppresses the anisotropy growth. In the last part of this work, numerical solutions are calculated and reveal a richer dynamic for the background, which contains one, two or even three bounce depending on the initial conditions and in the amount of anisotropy. |
