Gravitational waves generated from the cosmological QCD phase transition within AdS/QCD

M Ahmadvand,K Bitaghsir Fadafan

doi:10.1016/j.physletb.2017.07.039

Abstract

We study the gravitational waves produced by the collision of the bubbles as a probe for the cosmological first order QCD phase transition, considering heavy static quarks. Using AdS/QCD and the correspondence between a first order Hawking–Page phase transition and confinement–deconfinement phase transition, we find the spectrum and the strain amplitude of the gravitational wave within the hard and soft wall models. We postulate the duration of the phase transition corresponds to the evaporation time of the black hole in the five dimensional dual gravity space, and thereby obtain a bound on the string length in the space and correspondingly on the duration of the QCD phase transition. We also show that IPTA and SKA detectors will be able to detect these gravitational waves, which can be an evidence for the first order deconfinement transition.

Highlights

According to the standard cosmology, during the evolution of the universe, several Phase Transitions (PTs) have occurred
We study the gravitational waves produced by the collision of the bubbles as a probe for the cosmological first order QCD phase transition, considering heavy static quarks
We postulate the duration of the phase transition corresponds to the evaporation time of the black hole in the five dimensional dual gravity space, and thereby obtain a bound on the string length in the space and correspondingly on the duration of the QCD phase transition

Summary

INTRODUCTION

According to the standard cosmology, during the evolution of the universe, several Phase Transitions (PTs) have occurred. Numerical calculation indicates QCD PT at finite temperature for small and large quark masses was a first order PT [6]. The expectation value of Polyakov loop which can be read off from the heavy quark potential is the relevant order parameter for the confinement-deconfinement PT. We consider pure gauge theory with non-dynamical heavy quarks appropriate for Z(3) symmetry broken in the confinement-deconfinement PT with the expectation value of Polyakov loop as the order parameter. Employing the point that the confinement-deconfinement PT is corresponded to Hawking-Page PT [11] which is of a first order, we explain this PT in the AdS/QCD context and explore it through possible GWs generated during the transition..

GRAVITATIONAL WAVES AND THE FIRST ORDER COSMOLOGICAL QCD PHASE TRANSITION

Hard Wall

Soft Wall