Abstract
This is a contribution for the Proceedings of the Conference Hot Quarks 2016, held at South Padre Island, Texas, USA, 12-17 September 2016. I briefly review some thermodynamic and baryon transport results obtained from a bottom-up Einstein-Maxwell-Dilaton holographic model engineered to describe the physics of the quark-gluon plasma at finite temperature and baryon density. The results for the equation of state, baryon susceptibilities, and the curvature of the crossover band are in quantitative agreement with the corresponding lattice QCD results with 2 + 1 flavors and physical quark masses. Baryon diffusion is predicted to be suppressed by increasing the baryon chemical potential.
Highlights
Ultrarelativistic heavy ion collisions [1, 2, 3, 4, 5] constitute the experimental arena where many properties of deconfined QCD matter associated to the formation of a quark-gluon plasma (QGP) [6, 7, 8] are being currently uncovered at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC)
This fact may be attested by the very small value of the ratio between the shear viscosity (η) and the entropy density (s) of the fluid, η/s ≈ 0.095, obtained in hydrodynamic simulations of the spacetime evolution of the QGP simultaneously matching experimental data for different physical observables [11]. Such a small ratio is incompatible with perturbative QCD calculations of η/s [12, 13], but is remarkably close to the value η/s = 1/4π valid for any isotropic and translationally invariant gauge/gravity dual [14, 15, 16, 17] with two derivatives for the metric field in the gravity action [18, 19]. This fairly general and robust property of holographic plasmas implies that, in order to attempt to obtain phenomenologically reliable insights for the physics of the QGP, one must take into account the behavior of other physical observables besides η/s, since many different gauge/gravity duals describing very different strongly correlated quantum fluids share the same value of η/s
The super Yang-Mills (SYM) plasma is conformal, while the QGP is strongly non-conformal in the crossover region, which is precisely the region where, in principle, holographic plasmas could be useful for real-world phenomenology, since it is in this region where the QGP is strongly coupled
Summary
Ultrarelativistic heavy ion collisions [1, 2, 3, 4, 5] constitute the experimental arena where many properties of deconfined QCD matter associated to the formation of a quark-gluon plasma (QGP) [6, 7, 8] are being currently uncovered at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC). This fact may be attested by the very small value of the ratio between the shear viscosity (η) and the entropy density (s) of the fluid, η/s ≈ 0.095, obtained in hydrodynamic simulations of the spacetime evolution of the QGP simultaneously matching experimental data for different physical observables [11].
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