Eur. Phys. J. C (2011) 71: 1580
https://doi.org/10.1140/epjc/s10052-011-1580-y

Regular Article - Theoretical Physics

QCD phase transition in Brans–Dicke cosmology

Department of Physics, Shahid Beheshti University G. C., Evin, Tehran, 19839, Iran

^* e-mail: k-atazadeh@sbu.ac.ir

Received: 27 July 2010
Revised: 25 January 2011
Published online: 13 April 2011

Abstract

In the standard picture of cosmology, when the universe was about 10 μsec old it underwent a transition from quark phase to hadron one, being associated with a chiral symmetry breaking after the electro weak transition. We assume that this transition was of crossover and study the evolution of the Universe in the context of Brans–Dicke theory. The evolution of physical quantities relevant to the physical description of the early Universe, namely, the energy density, temperature and the scale factor, are studied within an effective model of lattice QCD for high temperature and also we consider in the context of hadronic resonance gas model those parameters at low temperature. We show that for different values of Brans–Dicke coupling, ω, a phase transition occurs and results in decreasing of the effective temperature of the quark–gluon plasma during the process of quark–hadron phase transition.