We consider a universe dominated by a relativistic Bose-Einstein condensate with a conserved charge quantum number. We show that the solution of the Einstein equations with the energy-momentum tensor of the condensate consists of an inflationary (de Sitter) expansion of the Universe. The cosmological constant is zero at all times in this model. We also discuss the question of transition from the inflationary to the radiation-dominated stage of the expansion.

• Received 26 May 1992

DOI:https://doi.org/10.1103/PhysRevD.47.416