Physics
Scientific paper
Jul 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998phdt........18s&link_type=abstract
Thesis (PHD). THE JOHNS HOPKINS UNIVERSITY , Source DAI-B 59/01, p. 261, Jul 1998, 135 pages.
Physics
Gravitation
Scientific paper
This dissertation is devoted to the study of phenomenology in neutrino physics and cosmology: gravitational effects on the neutrino oscillation, finite temperature effects on the neutrino decoupling in the early Universe, and a scale-dependent cosmology. The main results are: (1) The propagation and oscillation of neutrinos in a gravitational field are studied by calculating a covariant quantum-mechanical phase in a curved spacetime. Specifically, the cases of the radial propagation and the non-radial propagation in the Schwarzschild metric are considered. A possible application to gravitational lensing of neutrinos is also suggested. (2) Leading finite temperature effects on the neutrino decoupling temperature in the early Universe are studied. By modifying the dispersion relations and the phase space distribution functions due to the presence of the particles in the heat bath at temperature around MeV we have shown that the finite temperature effects increase the neutrino decoupling temperature by 4.4%, the largest contribution coming from the modification of the phase space distribution. (3) We propose a scale-dependent cosmology with a stress-energy tensor of viscous fluid, in which the Robertson-Walker metric and Einstein field equations are generalized in such a way that Ω0,/ H0 and the age of the Universe all become scale-dependent. Its implications on observations and possible modifications of the standard Friedmann cosmology are discussed, which suggest a picture of a Universe inside a highly dense and rapidly expanding shell with the underdense center. In this model, the linear Hubble diagram for nearby objects (z/ll1) remains valid. For large z, we present some numerical results of the luminosity distance and the mass density against the redshift. It is shown that the Hubble diagram in this model for a locally open Universe resembles to that of the flat Friedmann cosmology and Ω0 obs is an increasing function of the redshift.
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