Zero-frequency critical bulk viscosity: Is the amplitude ratio truly universal? art. no. 022201

It was shown by Onuki that the zero-frequency bulk viscosity is associated with a universal amplitude ratio that was calculated to be around 0.10. We show that the sound attenuation data can be used to extract a value for thi s universal number and we find this number to be around 0.18, reasonably cl ose to Onuki's estimate. However, we argue that a reconsideration of this a mplitude ratio shows that this ratio is not truly universal. It has a logar ithmic correction instead.