  String theoretical arguments led to the hypothesis that the ratio of
viscosity to entropy of any physical system has a lower bound. Strongly coupled
systems usually have a small viscosity compared to weakly coupled plasmas in
which the viscosity is proportional to the mean free path. In the case of a
one-component plasma the viscosity as a function of the coupling strength shows
a minimum. Here we show that the ratio of viscosity to entropy of a strongly
coupled one-component plasma is always above the lower bound predicted by
string theory.
