For the last few decades cosmology has played an important role in probing fundamental physics. Both neutrino mass and matter-antimatter asymmetry require extension of the standard model. On the other hand, the existence of dark matter and dark energy point towards physics beyond standard model, or a modification of general relativity. My research has been devoted to various issues in cosmology with beyond the standard model interactions, covering many questions, including the equation of state of dark energy, connections between dark matter and dark energy, and the origin of matter in the universe.

Our ignorance about dark energy can be nicely parametrized by its equation of state w. An exciting possibility is w < -1, as indicated by the “Gold” SNIa data set. Devising consistent models with w < -1 has proven to be challenging. I showed that w < -1 naturally arises if quintessence interacts with dark matter.

A second research program is to consider the question: can dark matter and dark energy be manifestations of same fundamental particle? The strongest motivation for this is the similarity of the energy densities of DE and DM at the present epoch. I considered a scalar field which at some point in the history of the universe transitions to a dark matter state. I have shown that “Late Forming Dark Matter” (LFDM), may arise in this set up. Such phenomena can arise in hybrid neutrino dark energy models, whose phenomenology I also consider.

Finally, electroweak baryogenesis is a appealing candidate to explain the origin of the matter in our universe. However, with this mechanism, to generate the observed asymmetry one requires a strong first order phase transition. This, in turn, predicts that the Higgs mass should be less than 65 GeV, in conflict with experimental limits. I studied a scenario where the presence of a light scalar can keep the Higgs mass above the experimental limit and also make the phase transition strong and first order. I also studied the possibility of gravity waves from such phase transition, which are in general too small to be observed.