Suppression of Baryon Diffusion and Transport in a Baryon Rich Strongly Coupled Quark-Gluon Plasma

Five dimensional black hole solutions that describe the QCD crossover transition seen in $(2+1)$-flavor lattice QCD calculations at zero and nonzero baryon densities are used to obtain predictions for the baryon susceptibility, baryon conductivity, baryon diffusion constant, and thermal conductivity of the strongly coupled quark-gluon plasma in the range of temperatures $130\mathrm{MeV}\le T\le 300\mathrm{MeV}$ and baryon chemical potentials $0\le {\mu }_B\le 400\mathrm{MeV}$. Diffusive transport is predicted to be suppressed in this region of the QCD phase diagram, which is consistent with the existence of a critical end point at larger baryon densities. We also calculate the fourth-order baryon susceptibility at zero baryon chemical potential and find quantitative agreement with recent lattice results. The baryon transport coefficients computed in this Letter can be readily implemented in state-of-the-art hydrodynamic codes used to investigate the dense QGP currently produced at RHIC’s low energy beam scan.

Figure 1

Second- and fourth-order baryon susceptibilities at ${\mu }_B=0$ in our holographic model compared with lattice data from Ref. [56].

Figure 2

Baryon susceptibility (top left), baryon dc conductivity (top right), baryon diffusion constant (bottom left), and thermal conductivity (bottom right) as functions of the temperature for different values of the baryon chemical potential. The corresponding conformal values attained at large $T$ (and ${\mu }_B=0$) are also shown.