Fate of Z_2 symmetric scalar condensates in the early Universe

by Wenyuan Ai (King's College London)

Thursday 9 Nov 2023, 14:00 → 15:00 Europe/Berlin

HS3 (Physikdepartment)

Scalar condensates are common objects in cosmology, existing in various forms (strings, domain walls, oscillating condensates). In this talk, I will discuss the evolution of $Z_2$ symmetric, oscillating homogeneous scalar condensates in the early Universe from first principles using non-equilibrium quantum field theory. We show that the decay of such scalar condensates cannot be complete because their decay rates always decrease faster than the Hubble parameter at sufficiently late times. This is due to either the amplitude dependence or the temperature dependence in the condensate decay rates. This incomplete decay of $Z_2$ scalar condensates is reminiscent of the freeze-out process of ordinary particles. Consequently, such oscillating scalar condensates make an irreducible contribution to the dark matter relic abundance unless they fragment.