QCD equation of state and cosmological parameters in the early universe

Abstract

The time evolution of cosmological parameters in early Universe at the deconfinement transition is studied by an equation of state (EoS) which takes into account the finite baryon density and the background magnetic field. The non perturbative dynamics is described by the Field Correlator Method (FCM) which gives, with a small number of free parameters, a good fit of lattice data. The entire system has two components, i.e. the quark-gluon plasma and the electroweak sector, and the solutions of the Friedmann equation show that the scale factor, a(t), and H(t) = (1/a)da/dt are weakly dependent on the EoS, but the deceleration parameter, q(t), and the jerk, j(t), are strongly modified above the critical temperature T c , corresponding to a critical time t c ≃ 20 − 25µs. The time evolution of the cosmological parameters suggest that above and around T c there is a transient state of acceleration typical of a matter dominated Universe; this is entailed by the QCD strong interaction driven by the presence of massive colored objects.

Finite temperature QCD four-point function in the presence of a weak magnetic field within the hard thermal loop approximation

“…A lot of work has been done to study the QCD EoS in the absence of any background magnetic field using both the nonperturbative method like Lattice QCD (LQCD) [49][50][51][52] and also the hard thermal loop (HTL) resummed perturbation theory [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72]. Recently, the QCD EoS in the presence of magnetic field * Najmul.Haque@theo.physik.uni-giessen.de has been studied using LQCD [73,74], the hadron resonance gas model [75], the field correlator method [76], the Polyakov linear-sigma model [77], and also the perturbation theory in two-loop order [78]. Very recently, in Ref.…”

Deconfinement transition effects on cosmological parameters and primordial gravitational waves spectrum

“…Since the cosmological parameters can depend on the higher order derivatives of the Hubble parameter, i.e., on the higher order derivative of the thermodynamical quantities, it could be possible that some effects show up near the critical temperature [4].…”

“…(38), we set boundary conditions at high temperature, such as 10 4 MeV, where the modes h k are given by the radiation era solutions [Eq. (30)].…”

“…which involve the derivatives of the scale factor aðtÞ [4]. Indeed, the fluctuations of the cosmological parameters with higher order derivatives are strongly enhanced by the phase transition.…”

“…Previous analyses [4,[8][9][10] considered the evolution of the first cosmological parameters (q, j) and of the energy density fluctuations during the deconfinement transition by a specific parametrization of the QCD equation of state (EoS) or less recent lattice data.…”