Preinflationary dynamics of power-law potential in loop quantum cosmology

In this article, I mainly discuss the dynamics of the pre-inflationary Universe for the potential $V(\phi) \propto \phi^n$ with $n=5/3$ in the context of loop quantum cosmology, in which the big bang singularity is resolved by a non-singular quantum bounce. In the case of the kinetic energy-dominated initial conditions of the scalar field at the bounce, the numerical evolution of the Universe can be split up into three regimes: {\em bouncing, transition,} and {\em slow-roll inflation}. In the bouncing regime, the~numerical evolution of the scale factor does not depend on a wide range of initial values, {or on}~the inflationary potentials. I calculate the number of $e$-folds in the slow-roll regime, by which observationally identified initial conditions are obtained. Additionally, I display the phase portrait for the model under consideration.Comment: 6 pages, 2 figures, 1 table. This article is based on the talk given in International Conference on Quantum Gravity, SUSTech, Shenzhen, China, 26-28 March 201

Late-time acceleration with steep exponential potentials

In this letter, we study the cosmological dynamics of steeper potential than exponential. Our analysis shows that a simple extension of an exponential potential allows to capture late-time cosmic acceleration and retain the tracker behavior. We also perform statefinder and $Om$ diagnostics to distinguish dark energy models among themselves and with $\Lambda$CDM. In addition, to put the observational constraints on the model parameters, we modify the publicly available CosmoMC code and use an integrated data base of baryon acoustic oscillation, latest Type Ia supernova from Joint Light Curves sample and the local Hubble constant value measured by the Hubble Space Telescope.Comment: 9 pages, 5 figures, 2 table

Cosmic acceleration from coupling of baryonic and dark matter components: Analysis and diagnostics

In this paper, we examine a scenario in which late-time cosmic acceleration might arise due to the coupling between baryonic matter and dark matter without the presence of extra degrees of freedom. In this case, one can obtain late-time acceleration in Jordan frame and not in Einstein frame. We consider two different forms of parametrization of the coupling function, and put constraints on the model parameters by using an integrated datasets of Hubble parameter, Type Ia supernova and baryon acoustic oscillations. The models under consideration are consistent with the observations. In addition, we perform the statefinder and $Om$ diagnostics, and show that the models exhibit a distinctive behavior due to the phantom characteristic in future which is a generic feature of the underlying scenario.Comment: 15 pages, 5 figure