* Title: Dynamics of the Peccei-Quinn field in early universe
* Speaker: Masahiro Takimoto (The University of Tokyo) (at CTPU Seminar room)
* Date: 3:00~4:00 PM, 25 Feb 2016
* Abstract: We consider the cosmology of the Peccei-Quinn(PQ) models paying particular attention to the dynamics of the scalar field which have PQ charge. If PQ charge is restored at some epoch, the scalar field starts to oscillate later. Such oscillating scalar field may dominantly decay into relativistic axion particles which become a dark radiation component of the universe, whose energy density is tightly bounded. We clarify in what circumstances the axion overproduction is avoided taking the thermal dissipation effects into account. We show that owing to the thermal dissipation effects, the axion overproduction is avoided even when the scalar field once dominates the universe.