Seemingly different physical systems may exhibit universal behavior. For instance, certain properties of water vapor close to its boiling point or the behavior of a magnet close to the temperature in which it looses its magnetization are identical near the phase transition.
In a recent paper E. Shaverin and A. Yarom studied a different notion of universality. Using the gauge-gravity correspondence they considered various types of generalized viscosities which characterize conformal fluids that can be described by a black hole dual. Generically, these viscosities are not universal and depend on the particle content of the theory. However, a certain linear combination of these generalized viscosities does seem to exhibit universal behavior. In particular, it has been shown that within the context of theories whose kinetic terms have two derivatives, this linear combination does not depend on the particle content of the theory. In their recent work the Shaverin and Yarom have shown that the linear combination of viscosities vanishes even beyond two derivative gravity, at least in a subset of possible extensions of the gravitational action. This is in contrast to the behavior of the ratio of the shear viscosity to entropy density which was thought to be universal but has been found to deviate from its universal behavior once the gravitational action includes perturbative terms which involve more than two derivatives.