We present the full nonlinear calculation of the formation of a Q ball through the Affleck-Dine (AD) mechanism by numerical simulations. It is shown that large Q balls are actually produced by the fragmentation of the condensate of a scalar field whose potential is very flat. We find that the typical size of a Q ball is determined by the most developed mode of linearized fluctuations, and almost all the initial charges which the AD condensate carries are absorbed into the formed Q balls, whose sizes and the charges depend only on the initial charge densities.

• Received 4 November 1999

DOI:https://doi.org/10.1103/PhysRevD.61.041301