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Title: Beyond the standard cosmological paradigm with weak gravitational lensing
Author: Leonard, Catherine Danielle Bartlett
ISNI:       0000 0004 6496 1863
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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Next-generation cosmological surveys will demand an unprecedented understanding of the interplay between theoretical and observational aspects of weak gravitational lensing. This thesis presents a study of the parameter degeneracies and theoretical uncertainties which will affect weak lensing tests of cosmology beyond the standard paradigm. In particular, tests of alternative theories of gravity and of spatial curvature are considered. First, by considering linear-order departures from the standard gravitational theory of general relativity, a novel expression is derived for the weak lensing convergence power spectrum under alternative theories of gravity. Using this expression, degeneracies between gravitational parameters in weak lensing observations are explored, first with a focus on scale-independent parameterisations of gravity, then considering new physical scales introduced by alternative theories. The degeneracy-breaking offered by the combination of weak lensing and redshift-space distortions is shown to be robust to the time-dependence of the functions parameterising modified gravity. Next, the gravity-testing statistic EG is investigated, and a new theoretical expression for its observationally-motivated definition is presented. The theoretical uncertainty of EG is compared to forecast statistical errors, and found to be significant in the case of a more futuristic measurement. Predictions are then computed for EG under deviations from general relativity, and the ongoing utility of EG as a probe of gravity is discussed. Finally, an investigation is made of the potential for measuring or constraining the spatial curvature using weak lensing and complementary observables. The predicted constraint on the spatial curvature is forecast for a suite of upcoming surveys, and the effect of including parameters which may be degenerate with the spatial curvature is explored. It is found that upcoming observations are likely to constrain spatial curvature at a 10⁻³ level, but not to reach the best-case constraint of ~10⁻⁴.
Supervisor: Ferreira, Pedro G. ; Miller, Lance Sponsor: Rhodes Trust ; Natural Sciences and Engineering Research Council of Canada
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Standard model (Nuclear physics) ; Dark energy (Astronomy) ; Neutrinos