Leiden University Student Repository

Sabti, Nashwan (2016)

Constraining Cosmological Parameters Using the CLASS Code

Bachelor thesis | Natuurkunde (BSc)

Cosmological probes come in a large variety of forms and unveil many characteristics of the Universe. The extraction of cosmological parameters from probes, such as the cosmic microwave background, is done by fitting predictions of cosmological models to data. This requires the use of Boltzmann codes that possess powerful and efficient mechanisms for producing cosmological predictions. In this thesis the cosmological parameter extraction code CLASS is used to constrain primarily the energy densities and the Hubble parameter of the Universe. Four independent datasets that together probe the Universe at a large range of scales are used for this purpose. The data analysis is done within the framework of two different LCDM cosmological models. A stepwise description of a data analysis within the framework of a LWDM model is also provided. It is shown how combining independent datasets can break degeneracies between cosmological parameters, which is necessary to explore signatures of...Show moreCosmological probes come in a large variety of forms and unveil many characteristics of the Universe. The extraction of cosmological parameters from probes, such as the cosmic microwave background, is done by fitting predictions of cosmological models to data. This requires the use of Boltzmann codes that possess powerful and efficient mechanisms for producing cosmological predictions. In this thesis the cosmological parameter extraction code CLASS is used to constrain primarily the energy densities and the Hubble parameter of the Universe. Four independent datasets that together probe the Universe at a large range of scales are used for this purpose. The data analysis is done within the framework of two different LCDM cosmological models. A stepwise description of a data analysis within the framework of a LWDM model is also provided. It is shown how combining independent datasets can break degeneracies between cosmological parameters, which is necessary to explore signatures of beyond standard model physics. Furthermore, a consistency check between CLASS and a second, independent Boltzmann code is performed and discussed.Show less

Cosmology

CLASS

CAMB-wdm

Author

Sabti, Nashwan

Faculty

Faculty of Science

Specialisation

BSc Physics & Astronomy

Supervisors

Boyarsky, Alexey
Kuijken, Koenraad

ECTS Credits

3

Language

en