Observational constraints on dark energy cosmological model parameters

Date

2013-10-09

Journal Title

Journal ISSN

Volume Title

Publisher

Kansas State University

Abstract

The expansion rate of the Universe changes with time, initially slowing (decelerating) when the universe was matter dominated, because of the mutual gravitational attraction of all the matter in it, and more recently speeding up (accelerating). A number of cosmological observations now strongly support the idea that the Universe is spatially flat (provided the dark energy density is at least approximately time independent) and is currently undergoing an accelerated cosmological expansion. A majority of cosmologists consider ``dark energy" to be the cause of this observed accelerated cosmological expansion.

The standard" model of cosmology is the spatially-flat $\Lambda$CDM model. Although most predictions of the $\Lambda$CDM model are reasonably consistent with measurements, the $\Lambda$CDM model has some curious features. To overcome these difficulties, different Dark Energy models have been proposed. Two of these models, the XCDM parametrization and the slow rolling scalar field model $\phi$CDM, along with standard" ΛCDM, with the generalization of XCDM and ϕCDM in non-flat spatial geometries are considered here and observational data are used to constrain their parameter sets.

In this thesis, we start with a overview of the general theory of relativity, Friedmann's equations, and distance measures in cosmology. In the following chapters we explain how we can constrain the three above mentioned cosmological models using three data sets: measurements of the Hubble parameter H(z), Supernova (SN) apparent magnitudes, and the baryonic acoustic oscillations (BAO) peak length scale, as functions of redshift z. We then discuss constraints on the deceleration-acceleration transition redshift zda using unbinned and binned H(z) data. Finally, we incorporate the spatial curvature in the XCDM and ϕCDM model and determine observational constraints on the parameters of these expanded models.

Description

Keywords

Cosmology constraints, Dark energy, Constraints

Graduation Month

December

Degree

Doctor of Philosophy

Department

Department of Physics

Major Professor

Bharat Ratra

Date

2013

Type

Dissertation

Citation