The Cosmological Constant Problem and Role of Neutrino Mass in Changing the Expansion Rate of the Universe

Abstract

In this thesis it's found that the universe expansion might be accelerating. In other words it is made to expand by a new strange kind of energy, and that the cosmological constant assumed by Elbert Einstein to represent this strange shape of the potential energy in the space is one of two competitive alternatives for explaining changes in universe expansion rate. The accumulative evidence explains that the universe structure of matter is less than the one expected by inflation theory of the universe so that the universe is moving towards expanding in exceeding rate rather than expected by theory, and the average energetic density of the universe leads to another opinion about the future of the universal either to be closed, and in this case the expansion will be stopped, or to be open so it will be expanded forever. Study also clarifies the importance of the cosmological constant assumed by Einstein for its direct relation with dark energy that was discovered by scientists, and assumes that the neutrino contributes in a way to this dark energy. At this concept the study explain through the reaction of the fossil (relic) neutrino with the electron that the energetic density of the relic neutrino and antineutrino is so minute compared to the critical energetic density, hence its influence in the cosmological constant is very little so the common concept of inflation of the universe expansion is still dominating. This study also explains that the energetic density of the relic neutrino resulting from the electron-positron annihilation into neutrino-antineutrino pair with the contribution of the free electromagnetic influences is of the order, and this result compared to the critical value of density order of is is thought to be having some contribution to dark energy and then to the cosmological constant as well. That is after deciding about the value of the neutrino mass. This contribution may play an important role in changing our views with respcet to the concept of the universe expansion at present.