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.
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