Probing gravity and the neutrinos with cosmology.
Doctoral thesis, UCL (University College London).
This thesis is related to the growth of structure in the late-time Universe. It addresses both the measurement of this structure and the use of such information in constraining fundamental underlying physics. This includes the gravitational framework and the sum of the three neutrinos’mass. The thesis starts by using weak gravitational lensing data (CFHTLS) to constrain a modification of gravity that is invoked to provide the observed accelerated expansion in the Universe. This is shown to disfavour the model in question. It is, however, incapable of placing any bounds on the growth parameter that represents extensions to gravity. The future of weak lensing in probing general relativity is illustrated with forecasts on the growth signature and power spectrum parameter using the proposed Euclid probe. A measurement is made on the clustering of Luminous Red Galaxies (LRGs) in the Universe. This represents a new photometric galaxy clustering angular power spectrum: MegaZ LRG Data Release 7 (DR7). The cosmological constraints are demonstrated to be competitive with spectroscopic surveys and complementary to the WMAP5 data. Specifically, bounds of f_b \equiv \Omega _b / \Omega _m = 0.173 \pm 0.046 and \Omega_m = 0.260 \pm 0.035 are placed. Potential systematics in the data are discussed and examined. The work concludes by placing one of the most stringent constraints available of the sum of the three neutrino masses. By combining cosmic microwave background information, distance measures from supernovae and baryon acoustic oscillations with growth from the MegaZ LRG galaxy clustering data, produced earlier, the limit is found to be \sum m_v < 0.281 eV at the 95% confidence level.
|Title:||Probing gravity and the neutrinos with cosmology|
|Open access status:||An open access version is available from UCL Discovery|
|Additional information:||The abstract contains LaTeX text. Please see the attached pdf for rendered equations|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Physics and Astronomy|
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