title: Holographic viscosity of fundamental matter.
abstract: A holographic dual of a finite-temperature SU(Nc) gauge theory with a small number of flavors Nf<<Nc typically contains D-branes in a black hole background. By considering the backreaction of the branes, we demonstrate that, to leading order in Nf/Nc, the viscosity to entropy ratio in these theories saturates the conjectured universal bound eta/s> or =1/4pi. Given the known results for the entropy density, the contribution of the fundamental matter eta fund is therefore enhanced at strong 't Hooft coupling lambda; for example, eta fund approximately lambda NcNfT3 in four dimensions. Other transport coefficients are analogously enhanced. These results hold with or without a baryon number chemical potential.
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: David
authors.initials: D
authors.lastname: Mateos
authors.forename: Robert C
authors.initials: RC
authors.lastname: Myers
authors.forename: Rowan M
authors.initials: RM
authors.lastname: Thomson