Cosmological constraints on neutrinos

Abstract

Neutrino cosmology has been a research area of interests in recent years. From the information related to neutrinos left from the Cosmic Microwave Background (CMB), we could learn things in different epochs during the evolution of the Universe. Mostly, N_eff and sigma m_nu are the parameters to constrain neutrinos from observations. The underlying physics background of these two parameters can help us answer the following questions: how much do neutrinos account for the total energy density of the present Universe? Do they behave as massive particles or as radiation at the present time? Does the Universe that we live in have more neutrino species than what we have detected, or is there just a tiny fraction of them in the Universe? In this thesis, the constraints on N_eff and sigma m_nu are investigated in models that include active and sterile neutrinos. The results were obtained by performing parameter estimations by using the CosmoMC code, the Planck 2015 and 2018 data.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Richard Battye (Supervisor) & Rene Breton (Supervisor)