Effect of an extrinsic curvature on a quark–hadron phase transition

Abstract

The last phase transition predicted by the standard model of particle physics took place at the QCD scale T ∼ 200 MeV when the universe was about t ∼ 10−5 s old and the Hubble radius was around 10 km. In this paper, we consider the quark–hadron phase transition in the context of braneworld cosmology where our universe is a 3-brane embedded in an m-dimensional bulk and localization of matter on the brane is achieved by means of a confining potential. We study the behavior of the physical quantities relevant to the description of the early universe such as the energy density, temperature and scale factor, before, during and after the phase transition and investigate the effects of an extrinsic curvature on the cosmological phase transition. We show that the braneworld effects reduce the effective temperature of the quark–gluon plasma and of the hadronic fluid. Finally, we discuss the case where the universe evolved through a mixed phase with a small initial supercooling and monotonically growing hadronic bubbles.