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Scalar-Tensor Theories for Dark Energy and their Cosmological Consequences

Sculthorpe, Gregory (2014) Scalar-Tensor Theories for Dark Energy and their Cosmological Consequences. PhD thesis, University of Sheffield.

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Abstract

One of the major outstanding questions in cosmology today is the nature of dark energy, the cause of the observed recent accelerated expansion of the universe. This thesis considers scalar-tensor theories as a possible candidate for dark energy and explores their observational consequences. The evolution equations for perturbation equations of a fluid, either relativistic or non-relativistic, disformally coupled to the scalar field are derived for the first time. A new observational probe for such theories, CMB μ-distortion, is then investigated. The effects of screened models of modified gravity on the CMB angular power spectrum are considered, looking at the potential for these to provide constraints on the models, even after imposing constraints coming from local tests and BBN. Finally, in the context of coupled quintessence, the initial conditions for general perturbation modes are derived with a view to determining whether the constraint on the coupling strength may be relaxed when the assumption of adiabatic initial conditions is lifted.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Science (Sheffield)
The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematics and Statistics (Sheffield)
Identification Number/EthosID: uk.bl.ethos.617203
Depositing User: Mr Gregory Sculthorpe
Date Deposited: 11 Aug 2014 14:11
Last Modified: 03 Oct 2016 11:17
URI: http://etheses.whiterose.ac.uk/id/eprint/6614

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