Danning Li

Thermodynamics of deformed AdS 5 model with a positive/negative quadratic correction in graviton-dilaton system

By solving the Einstein equations of the graviton coupling with a real scalar dilaton field, we establish a general framework to self-consistently solve the geometric background with black-hole for any given phenomenological holographic models. In this framework, we solve the black-hole background, the corresponding dilaon field and the dilaton potential for the deformed AdS5 model with a positive/negative quadratic correction. We systematically investigate the thermodynamical properties of the deformed AdS5 model with a positive and negative quadratic correction, respectively, and compare with lattice QCD on the results of the equation of state, the heavy quark potential, the Polyakov loop and the spatial Wilson loop. We find that the bulk thermodynamical properties are not sensitive to the sign of the quadratic correction, and the results of both deformed holographic QCD models agree well with lattice QCD result for pure SU(3) gauge theory. However, the results from loop operators favor a positive quadratic correction, which agree well with lattice QCD result. Especially, the result from the Polyakov loop excludes the model with a negative quadratic correction in the warp factor of AdS5.

A hQCD model and its phase diagram in Einstein-Maxwell-Dilaton system

A bstractBy use of the potential reconstruction approach we obtain a series of asymptotically AdS (aAdS) black hole solutions in an Einstein-Maxwell-Dilaton (EMD) system. Basing on the solutions of the system, we reconstruct a semi-analytical holographic QCD (hQCD) model with a quadratic term in warped factor. We discuss some aspects of the hQCD model, in particular we calculate the free energy of two static color sources (a heavy quark-antiquark pair) which is an important order parameter to describe confinement/deconfinement phase transition. The behavior of the free energy with respect to temperature and chemical potential is studied. We find that in the hQCD model the deconfinement phase transition can be realized and a critical point occurs. The resulting phase diagram in the temperature-chemical potential T − μ plane is in quite good agreement with the one from recent lattice results and effective models of QCD.

A dynamical soft-wall holographic QCD model for chiral symmetry breaking and linear confinement

A self-consistent dynamical soft-wall holographic QCD model is formulated in the framework of graviton–dilaton–scalar system, which can realize both chiral symmetry breaking and confinement, two of the most important phenomena of QCD. The scalar field corresponds to the quark–antiquark condensate and can explain the property of chiral dynamics. The quadratic dilaton background field ϕ=μ2z2 as in the original soft-wall model can accommodate two aspects in the manifestation of color confinement, i.e. the Regge spectra of hadrons and the linear potential between quarks. It is observed that both the slope of the Regge spectra and the string tension of the quark potential are proportional to μ2. More interesting observation is that the best fitted value of μ is around the dynamical gluon mass extracted from lattice data. It is also shown that the negative dilaton background ϕ=−μ2z2 can be safely excluded in this framework.

Dynamical holographic QCD model for glueball and light meson spectra

A bstractIn this work, we offer a dynamical soft-wall model to describe the gluodynamics and chiral dynamics in one systematical framework. We firstly construct a quenched dynamical holographic QCD (hQCD) model in the graviton-dilaton framework for the pure gluon system, then develop a dynamical hQCD model for the two flavor system in the graviton-dilaton-scalar framework by adding light flavors on the gluodynamical background. For two forms of dilaton background field

Enhancement of jet quenching around phase transition: result from the dynamical holographic model

\Phi =\mu_G^2{z^2}

Entanglement temperature in non-conformal cases

and

Chiral phase transition in the soft-wall model of AdS/QCD

\Phi =\mu_G^2{z^2} \tanh \left( {{{{\mu {{{_{{{G^2}}}^4}}^z}^2}} \left/ {{\mu_G^2}} \right.}} \right)

Realization of chiral symmetry breaking and restoration in holographic QCD

, the quadratic correction to dilaton background field at infrared encodes important non-perturbative gluodynamics and naturally induces a deformed warp factor of the metric. By self-consistently solving the deformed metric induced by the dilaton background field, we find that the scalar glueball spectra in the quenched dynamical model is in very well agreement with lattice data. For two flavor system in the graviton-dilaton-scalar framework, the deformed metric is self-consistently solved by considering both the chiral condensate and nonperturbative gluodynamics in the vacuum, which are responsible for the chiral symmetry breaking and linear confinement, respectively. It is found that the mixing between the chiral condensate and gluon condensate is important to produce the correct light flavor meson spectra. The pion form factor and the vector couplings are also investigated in the dynamical hQCD model. Besides, we give the criteria for the existence of linear quark potential from the metric structure, and show a negative quadratic dilaton background field is not favored in the graviton-dilaton framework.

Temperature dependent transport coefficients in a dynamical holographic QCD model

The phase transition and jet quenching parameter (q) over cap are investigated in the framework of the dynamical holographic QCD model. We find that both the trace anomaly and the ratio of the jet quenching parameter over cubic temperature (q) over cap /T-3 show a peak around the critical temperature T-c, and the ratio of the jet quenching parameter over entropy density (q) over cap / s sharply rises at T-c. This indicates that the jet quenching parameter can characterize the phase transition. The effect of the jet quenching parameter enhancement around the phase transition on the nuclear modification factor R-AA and elliptic flow upsilon(2) are also analyzed, and we find that the temperature-dependent jet quenching parameter from the dynamical holographic QCD model can considerably improve the description of jet quenching azimuthal anisotropy as compared with the conformal case.

Inverse magnetic catalysis in the soft-wall model of AdS/QCD

A bstractPotential reconstruction can be used to find various analytical asymptotical AdS solutions in Einstein dilation system generally. We have generated two simple solutions without physical singularity called zero temperature solutions. We also proposed a numerical way to obtain black hole solution in Einstein dilaton system with special dilaton potential. By using this method, we obtain the corresponding black hole solutions numerically and investigate the thermal stability of the black hole by comparing the free energy of thermal gas and the corresponding black hole. In two groups of non-conformal gravity solutions obtained in this paper, we find that the two thermal gas solutions are more unstable than black hole solutions respectively. Finally, we consider black hole solutions as a thermal state of zero temperature solutions to check that the first thermal dynamical law exists in entanglement system from holographic point of view.