Abstract
Particle-number-violating interactions wash out the primordial asymmetry of the particle number density generated by some interaction satisfying Sakharov conditions for baryogenesis. In this paper, we study how the primordial asymmetry evolves in time under the presence of particle-number-violating interactions and in the environment of an expanding universe. We introduce a complex scalar model with particle-number-violating mass terms and calculate the time evolution of the particle number density with nonequilibrium quantum field theory. We show how the time evolution of the number density depends on parameters, including the chemical potential related to the particle number, temperature, the size of the particle-number-violating mass terms, and the expansion rate of the universe. The number density behaves differently depending upon whether the chemical potential is larger or smaller than the rest mass of the scalar particle. When the chemical potential is smaller than the mass, the interference among the contribution of oscillators with various momenta reduces the number density in addition to the dilution due to the expansion of the universe. In the opposite case, the oscillation of the particle number density lasts for a long time and the cancellation due to the interference does not occur.
3 More- Received 8 March 2014
DOI:https://doi.org/10.1103/PhysRevD.90.016008
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