Observational constraints on dark energy parameters

 Our universe is undergoing an accelerated expansion, this has been confirmed by
various observations. The acceleration is caused by a component of the universe with
a large negative pressure called dark energy, which contributes to almost three-quarters of the total energy of the universe. The nature of dark energy is still a mystery for cosmologists. A large number of models have been proposed to explain it. The models include the cosmological constant which is favoured by large number of observations and also is the most elegant explanation of dark energy. Theoretically, this model suffers from the fine tuning problem. To circumvent this problem, many other models were proposed and have been studied in order to understand dark energy. These models include barotropic fluid model, scalar field models and many more. The simplest extension to cosmological constant is to assume dark energy to be a barotropic fluid. We discuss fluid models of dark energy, and extend our analysis to canonical scalar field models. To study these models, we solve the cosmological equations for the models and determine their respective parameters using different datasets. We focus mainly on the low redshift data constraints, namely Supernova type Ia data, Baryon Acoustic Oscillation data and direct measurements of Hubble parameter dataset. We have also combined the first two approaches and study the form of potentials which are consistent with different parameterisations. We reconstruct the Quintessence and Phantom scalar field potentials and study the evolution of the scalar field as a function of scale factor. Using the three observations mentioned earlier, we provide constraints on the reconstructed potential and field parameters.