Abstract
Modern concordance cosmology is faced with two tasks: Accounting for the abundance of the known constituents, and determining the nature of the unknown components — dark matter and dark energy. These make up approximately 30% and 70% of the current mass-energy budget. The nature of these components is unknown. The initial conditions which led to structure formation pose another important question. This thesis is based on a method which could, given data from future surveys, determine the nature of dark energy through its equation of state and its evolution, and advance our understanding of the distribution of the primordial density .uctuations.
The method used in this thesis is weak gravitational lensing. We use information from tomographic cosmic shear, which acts as a sensitive probe of cosmological parameters by measuring the mass distribution and the geometry of the low redshift Universe. This thesis studies the potential of an all-sky weak lensing tomographic survey to obtain joint constraints for di.erent sets of cosmological parameters describing dark energy, massive neutrinos (hot dark matter), and the primordial power spectrum. Using the Fisher matrix formalism, we examine how the constraints vary as the parameter set is enlarged, and as the .ducial cosmology is changed. We also study the constraints when CMB priors are added to our weak lensing error forecasts.
We .nd that weak lensing with CMB priors provides robust constraints on dark energy parameters and can simultaneously provide strong constraints on all parameters. Thus, a future all-sky survey in conjunction with expected results from CMB anisotropy probes, could provide constraints on the dark energy equation of state parameters. Such a survey could also constrain the total neutrino mass and the number of massive neutrino species, as well as the primordial spectral index and its running.
The results presented in this thesis show that error forecasts from a future weak lensing survey are stable against the addition of parameters to the .ducial model, and that this stability is improved by adding CMB priors. This thesis also shows that the weak lensing error forecasts are robust against changes in the .ducial cosmological model.
Applying these methods to study their implications for the the planning of future surveys, we .nd that the design parameter which has the greatest impact on the precision is the survey area. We also show that future surveys will need to utilise a maximum multipole of 104 if they are to achieve their maximum potential. Our results show that the same optimisation strategy applies for dark energy, neutrino, and primordial power spectrum parameters.
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