Presentasjon av masteroppgave: Paul Anthony Frontéri
Cosmology of Symmetron Mass-Varying Neutrinos
In this thesis we investigate a dynamical cosmological constant called the quintessence. Quintessence is a scalar field varying in both space and time following a chosen po- tential. To explain the coincidence problem, e.g. why the expansion of the universe is accelerating now, we couple the scalar field to neutrinos. The coupling changes the constant neutrino mass to a mass varying neutrino that depends on the scalar field. However, this coupling causes a fifth force on the neutrinos creating to much clumping on large scales. We suggest to use the screening potential of the symmetron model to prevent this clumping. The symmetron forces the scalar field to zero at high neutrino densities and spontaneously breaks the potential at low neutrino densities making the scalar field active. We modified a standard code for the cosmological evolution (CAMB) to include both the mass varying neutrino and the symmetron. Adding an cosmological constant is still needed to achieve the observed late time accelerated expansion. Simulation where done for three dierent scenarios, depending on the occurrence of the symmetry breaking. There is a notable eect from the symmetron-neutrino coupling and larger eects as one increases the neutrino mass. However, for all scenarios one observe small changes compared with the standard LCDM.
Veileder: Professor David F. Mota, Institutt for teoretisk astrofysikk, UiO
Veileder: Postdoktor Signe Riemer-Sørensen, Institutt for teoretisk astrofysikk, UiO
Intern sensor: Professor Mats Carlsson, Institutt for teoretisk astrofysikk, UiO
Ekstern sensor: Postdoktor Jose Beltran Jimenez, Postdoc, Louvain University, Belgia