On The Observational Signature Of Interaction Between Dark Matter And Dark Energy And Tensor-Vector-Scalar Theory

The standard cosmological model, ACDM, is successful. It is compat-ible with most astrophysical observations. However, it suffers the cosmo-logical constant problem and fine-tuning problem. In this thesis, we will study two alternative cosmological models, focusing on their observational signature. We will try to find whether the models are compatible with the observations and distinguish them from ACDM.We first consider the interaction between dark matter and dark ener-gy. Confronting to Planck data, we conclude that the interaction is com-patible with the observations. Based on the analysis of the evolution of the gravitational potential, we propose two new observables, the peculiar velocities and the kSZ temperature power spectrum, which are sensitive to the interaction. The current data of these observables are compatible with the interacting dark energy model.In the second half of the thesis, we investigate Bekenstein’s TeVeS theory. We find that the evolution of perturbations in TeVeS cosmology is different from ACDM. We propose that the measurements of peculiar velocities, the kSZ power spectrum and growth factor can serve to distin-guish TeVeS and ACDM model. By fitting to Planck data, we conclude that TeVeS theory with Bekenstein’s original potential is ruled out by observations.