Spectra of glueballs and oddballs and the equation of state from holographic QCD
Lin Zhang, Chutian Chen, Yidian Chen, Mei Huang
Abstract
We study the spectra of two-gluon glueballs and three-gluon oddballs and corresponding equation of state in 5-dimensional deformed holographic QCD models in the gravity-dilaton system, where the metric, the dilaton field, and the dilaton potential are self-consistently solved from each other through the Einstein field equations and the equation of motion of the dilaton field. We compare the models by inputting the dilaton field, inputting the deformed metric, and inputting the dilaton potential, and find that with only 2 parameters, the 5-dimensional holographic QCD model predictions on glueballs/oddballs spectra, in general, are in good agreement with lattice results except three oddballs states ${0}^{+\ensuremath{-}}$, ${2}^{+\ensuremath{-}}$ and ${3}^{\ensuremath{-}\ensuremath{-}}$. From the results of glueballs/oddballs spectra at zero temperature and the equation of state at finite temperature, we observe that the model with quadratic dilaton field can simultaneously describe glueballs/oddballs spectra as well as the equation of state of pure gluon system. The model with quadratic ${A}_{E}(z)$ can describe glueballs/oddballs spectra, but its corresponding equation of state behaves more like ${N}_{f}=2+1$ quark matter, which is consistent with the dimension analysis at ultraviolet (UV) boundary. Our results suggest that the Einstein-Maxwell-dilaton model with the profile $\ensuremath{\phi}(z)={z}^{2}$ can be regarded as a candidate of dual theory of pure gluodynamics. Though it is still difficult to find the dual theory of full QCD, the existence of dual theory of pure gluodynamics would be quite encouraging.