The shear viscosity of gauge theory plasma with chemical potentials
  We consider strongly coupled gauge theory plasma with conserved global charges that allow for a dual gravitational description. We study the shear viscosity of the gauge theory plasma in the presence of chemical potentials for these charges. Using gauge theory/string theory correspondence we prove that at large 't Hooft coupling the ratio of the shear viscosity to the entropy density is universal. 
Paolo Benincasa, Alex Buchel, Roman Naryshkin