Black hole thermodynamics, Casimir effect and induced gravity

An analogy between the subtraction procedure in the Gibbons-Hawking Euclidean path integral approach to black hole thermodynamics and the Casimir effect is shown. Then a conjecture about a possible Casimir nature of the Gibbons-Hawking subtraction is made in the framework of Sakharov's induced gravity. In this framework it appears that the degrees of freedom involved in the Bekenstein-Hawking entropy can be naturally identified with zero-point modes of the matter fields. Some consequences of this view are sketched.