Aging of CKN: modulus versus conductivity analysis.

It was recently reported that the electrical modulus peaks narrows upon annealing of the ionic system CKN [Paluch et al., Phys. Rev. Lett. 110, 015702 (2013)], which was interpreted as providing evidence of dynamic heterogeneity of this glass. The present analysis of the same data in terms of the ac conductivity shows no shape changes, however. We discuss the relation between both findings and show further that the ac conductivity conforms to the prediction of the random barrier model at all times during the annealing.