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

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.Comment: v2: The effects of sound waves and the magnetohydrodynamic turbulence on the GW spectrum have been studied. Version published in PL

The cosmic QCD phase transition with dense matter and its gravitational waves from holography

Consistent with cosmological constraints, there are scenarios with the large lepton asymmetry which can lead to the finite baryochemical potential at the cosmic QCD phase transition scale. In this paper, we investigate this possibility in the holographic models. Using the holographic renormalization method, we find the first order Hawking-Page phase transition, between Reissner-Nordstr$\rm\ddot{o}$m AdS black hole and thermal charged AdS space, corresponding to the de/confinement phase transition. We obtain the gravitational wave spectra generated during the evolution of bubbles for a range of the bubble wall velocity and examine the reliability of the scenarios and consequent calculations by gravitational wave experiments.Comment: 18 pages , 4 figures, references and new discussions added, accepted to be published in Phys. Lett.

On meson melting in the quark medium

We consider a heavy quark-antiquark $(q\bar{q})$ pair as a heavy meson in the medium composed of light quarks and gluons. By using the AdS/CFT correspondence, the properties of this system are investigated. In particular, we study the inter-quark distance and it is shown that the mechanism of melting in the quark-gluon plasma and in the hadronic phase are the same. It is found that by considering finite coupling corrections, the inter-quark distance of a heavy meson decreases. As a result a heavy meson like $J/ \psi$ will melt at higher temperatures. By considering rotating heavy mesons, we discuss melting of exited states like $\chi_c$ and $\psi'$.Comment: 18 pages, 12 figures, We more clarify and extend the results of arXiv:0907.006

Rotating mesons in the presence of higher derivative corrections from gauge-string duality

We consider a rotating quark-antiquark $(q\bar{q})$ pair in $\mathcal{N}=4$ thermal plasma. By using AdS/CFT correspondence, the properties of this system have been investigated. We study variation of rotating string radius at the boundary as a function of the tip of U-shape string and angular velocity of rotating meson. We also extend the results to the higher derivative corrections i.e. ${\cal{R}}^2$ and ${\cal{R}}^4$ which correspond to finite coupling corrections on the rotating quark-antiquark system in the hot plasma. In ${\cal{R}}^4$ case and for fixed angular velocity as $\lambda^{-1}$ decreases the string endpoints get more and more separated. To study ${\cal{R}}^2$ corrections, rotating quark-antiquark system in Gauss-Bonnet background has been considered. We summarize the effects of these corrections in the conclusion section.Comment: 21 pages, 11 figures, NPB version, corrections to the effects of higher derivative term

Energy loss in a strongly coupled anisotropic plasma

We study the energy loss of a rotating infinitely massive quark moving, at constant velocity, through an anisotropic strongly-coupled N=4 plasma from holography. It is shown that, similar to the isotropic plasma, the energy loss of the rotating quark is due to either the drag force or radiation with a continuous crossover from drag-dominated regime to the radiation dominated regime. We find that the anisotropy has a significant effect on the energy loss of the heavy quark, specially in the crossover regime. We argue that the energy loss due to radiation in anisotropic media is less than the isotropic case. Interestingly this is similar to analogous calculations for the energy loss in weakly coupled anisotropic plasma.Comment: 26+1 pages, 10 figures, typos fixe

Heavy quarks in the presence of higher derivative corrections from AdS/CFT

We use the gauge-string duality to study heavy quarks in the presence of higher derivative corrections. These corrections correspond to the finite coupling corrections on the properties of heavy quarks in a hot plasma. In particular, we study the effects of these corrections on the energy loss and the dissociation length of a quark-antiquark pair. We show that the calculated energy loss of heavy quarks through the plasma increases. We also find in general that the dissociation length becomes shorter with the increase of coupling parameters of higher curvature terms.Comment: 22pages, 8 figures, Revised versio

Calculating the jet-quenching parameter in STU background

In this paper we use the AdS/CFT correspondence to compute the jet-quenching parameter in a N=2 thermal plasma. We consider the general three-charge black hole and discuss some special cases. We add a constant electric field to the background and find the effect of the electric field on the jet-quenching parameter. Also we include higher derivative terms and obtain the first-order correction for the jet-quenching parameter.Comment: 17 pages, 3 figures, revised versio