A k-essence Model Of Inflation, Dark Matter and Dark Energy

We investigate the possibility for \textit{k}-essence dynamics to reproduce the primary features of inflation in the early universe, generate dark matter subsequently, and finally account for the presently observed acceleration. We first show that for a purely kinetic \textit{k}-essence model the late time energy density of the universe when expressed simply as a sum of a cosmological constant and a dark matter term leads to a static universe. We then study another \textit{k}-essence model in which the Lagrangian contains a potential for the scalar field as well as a non-canonical kinetic term. We show that such a model generates the basic features of inflation in the early universe, and also gives rise to dark matter and dark energy at appropriate subsequent stages. Observational constraints on the parameters of this model are obtained.Comment: 8 pages, Latex, minor changes to match with published versio

Future deceleration due to cosmic backreaction in presence of the event horizon

The present acceleration of the universe leads to the formation of a cosmological future event horizon. We explore the effects of the event horizon on cosmological backreaction due to inhomogeneities in the universe. Beginning from the onset of the present accelerated era, we show that backreaction in presence of the event horizon causes acceleration to slow down in the subsequent evolution. Transition to deceleration occurs eventually, ensuring avoidance of a big rip.Comment: Latex, 5 pages, 2 figures. This version has small changes to match with the version published in MNRAS: Letter