Illuminating the Darkness: Using Alternative Parameterizations to Test Dark Energy Properties.

[摘要] In the first half of my dissertation, I study the effects of type Ia supernova (SNIa) systematic errors on dark energy using current data from the Supernova Legacy Survey. I consider how these systematics affect constraints from combined cosmological probes that include SNIa, baryon acoustic oscillations, and the cosmic microwave background. The temporal evolution of dark energy is described in terms of principal components of the equation of state, though simpler models are examined as well. The SNIa systematics are found to degrade the generalized figure of merit, which characterizes constraints in the multidimensional dark energy parameter space, by a factor of three to four. Nevertheless, overall constraints obtained on more than five principal components are very good with current data, even with the inclusion of known systematics.In the second half, I perform tests of the consistency of the standard wCDM model in the framework of General Relativity by separating out the information between geometry and growth of structure. Each late-universe dark energy parameter is replaced with two parameters: one describing geometrical information, and the other controlling the growth of structure. I use data from all principal cosmological probes to constrain both geometry and growth; of these, SNIa, baryon acoustic oscillations, and the cosmic microwave background primarily measure geometry, while cluster counts, weak gravitational lensing shear, and redshift space distortions constrain both geometry and growth. Both geometry and growth separately favor the LCDM cosmology with the matter density relative to critical Omega_M=0.3. Allowing the split equations of state to vary separately results in good agreement with the LCDM value (w=-1), with the major exception of redshift space distortions which favor less growth than in LCDM at 3-sigma confidence, favoring instead w^grow=-0.8. This preference by redshift space distortions for less growth has been noted previously and may be due to systematics, or be explained by the sum of the neutrino masses higher than that expected from the simplest mass hierarchies, m_nu=0.45 eV. Even in the new, larger parameter space the constraints are tight due to the impressive complementarity of different cosmological probes.

[发布机构] University of Michigan

[效力级别] growth of structure

[关键词] dark energy;growth of structure;cosmology;principal components;massive neutrinos;Physics;Science;Physics