A dilaton potential is adjusted to recently confirmed lattice QCD thermodynamics data in the temperature range $(0.7 ldots 3.5) T_c$ where $T_c = 155 text{MeV}$ is the pseudo-critical temperature. The employed holographic model is based on a gravity-
-single-field dilaton dual. We discuss conditions for enforcing (for the pure gluon plasma) or avoiding (for the QCD quark-gluon plasma) a first-order phase transition, but still keeping a softest point (minimum of sound velocity).
A gravity-scalar model in 5-dim. Riemann space is adjusted to the thermodynamics of SU(3) gauge field theory in the temperature range 1 - 10 $T/T_c$ to calculate holographically the bulk viscosity in 4-dim. Minkowski space. Various settings are compa
red, and it is argued that, upon an adjustment of the scalar potential to reproduce exactly the lattice data within a restricted temperature interval above $T_c$, rather robust values of the bulk viscosity to entropy density ratio are obtained.
Employing new precision data of the equation of state of the SU(3) Yang-Mills theory (gluon plasma) the dilaton potential of a gravity-dual model is adjusted in the temperature range $(1 - 10) T_c$ within a bottom-up approach. The ratio of bulk visco
sity to shear viscosity follows then as $zeta/eta approx pi Delta v_s^2$ for $Delta v_s^2 < 0.2$ and achieves a maximum value of $0.94$ at $Delta v_s^2 approx 0.3$, where $Delta v_s^2 equiv 1/3 - v_s^2$ is the non-conformality measure and $v_s^2$ is the velocity of sound squared, while the ratio of shear viscosity to entropy density is known as $(4 pi)^{-1}$ for the considered set-up with Hilbert action on the gravity side.
The expansion dynamics of hot electron-positron-photon plasma droplets is dealt with within relativistic hydrodynamics. Such droplets, envisaged to be created in future experiments by irradiating thin foils with counter-propagating ultra-intense lase
r beams, are sources of flashes of gamma radiation. Warm electron-positron plasma droplets may be identified and characterized by a broadened 511 keV line.
