An Oscillatory Quintessence Field as a Candidate for Dark Energy

Bandyopadhyay, Hirak (2016) An Oscillatory Quintessence Field as a Candidate for Dark Energy. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Hirak Bandyopadhyay (11MS003)) Hirak_MS_11MS003.pdf - Submitted Version Restricted to Repository staff only Download (442kB)

Abstract

In this thesis, we consider the dynamics of Oscillating scalar fields which are proposed as a model to solve the mystery of recent accelerated expansion of the universe. If the scalar field has oscillation frequency much greater than the expansion rate, it can be proposed as a plausible candidate for dark energy. In this model, we use two different potentials and try to understand the evolution of the ratio between the oscillation frequency and the Hubble expansion rate. For different conditions, we observe when the ratio of oscillation frequency and Hubble expansion rate crosses unity, and how it evolves throughout the time. We can show that, when the dark energy density decreases less rapidly than the background energy density, this ratio always increases with time. We understand all the possible cases of oscillations; early oscillation case refers where the crossover happens during the matter dominated era; no oscillation case suggests where the ratio is increasing but yet to reach unity. These cases are previously explored. We give more emphasis to the case when the ratio crosses unity after the quintessence field starts dominating. We examine this scenario with power law potential. Secondly, we use a hyperbolic potential to understand its dynamics and the possibility of getting late time acceleration from it. We try to simulate the evolution of deceleration parameter with redshift and try to show that the deceleration parameter changes from positive to negative at the redshift of z ~ 0:6, which is consistent with observation.

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