It is shown that the violation of the positiveness of the entropy due to the Casimir-Lifshitz interaction claimed in several papers is an artifact related to an improper interpretation of the "Casimir entropy", which actually is a difference of two positive terms. It is explained that at definite condition this "Casimir entropy" must be negative. A direct derivation of the low temperature behavior of the surface entropy of a metallic surface in conditions of the anomalous skin effect is given and singular temperature dependency of this quantity is discussed. In conclusion a hydrodynamic example of the entropy of a liquid film is considered. It occurs that the entropy of a film of finite thickness and a liquid half-space behave differently at T tends to 0.
@article{arxiv.1010.0537,
title = {Casmir-Lifshitz Forces and Entropy},
author = {Lev P. Pitaevskii},
journal= {arXiv preprint arXiv:1010.0537},
year = {2015}
}