Dynamical Dark Energy
2014Citations per year
0 Citations
Abstract: (submitter)
The ΛCDM model is considered to be the most successful cosmological model by
reason of its simplicity and of the quality of the fit that it provides to disparate types of data (SNeIa, CMB, BAO, etc.). According to this model, the current composition of the Universe is dominated by two fluids, the cold dark matter and the cosmological constant Λ, a form of dark energy with a constant energy density. In spite of its observational successes, the ΛCDM model is facing two difficulties, the cosmological constant problem and the coincidence problem. The cosmological constant problem is a discrepancy of about 120 orders of magnitude between the observed values of dark energy density and the value expected from quantum field computations. The coincidence problem relies on the observation that the energy densities of cold matter and of dark energy are currently of the same order of magnitude, although this could happen only during a narrow window of time in the ΛCDM model. A possible way to solve these two problems is to replace the cosmological constant by a dynamical form of dark energy whose density could vary in time. This thesis will be focusing on various aspects and different models of dynamical dark energy. More specifically, in chapters 2 and 3 we consider a model where dark energy and dark matter are coupled through an interaction term of the form Q0ρnΛ. We show that for n = 3/2, the ratio of the densities of dark energy and cold matter becomes constant at late time and thus possibly provides a solution to the coincidence problem. However, the values of
the model parameters consistent with the observational constraints disfavoured this solution. In chapter 4, we consider the proposed hypothesis that the dark energy should be in thermal equilibrium with the cosmological horizon and find the form of the interaction term Q required to maintain this equilibrium. Finally in chapter 5, based on studies of particles production from vacuum energy in de Sitter spacetime, we verify under which conditions this decay could affect the probability distribution of the values of the cosmological constant obtained from a modified version of the anthropic principle, the causal entropic principle.- dark energy: density
- energy: density
- density: ratio
- space-time: de Sitter
- vacuum state: energy
- cosmological constant
- dark matter
- cosmic background radiation
- field theory
- anthropic principle
References(256)
Figures(0)
- [1]
- [2]
- [3]
- [4]
- [5]
- [6]
- [7]
- [8]
- [9]
- [10]
- [11]
- [12]
- [13]
- [14]
- [15]
- [16]
- [17]
- [18]
- [19]
- [20]
- [21]
- [22]
- [23]
- [24]
- [25]