Which sequences of holes are admissible for periodic homogenization with Neumann boundary condition?

In this paper we give a general presentation of the homogenization of Neumann type problems in periodically perforated domains, including the case where the shape of the reference hole varies with the size of the period (in the spirit of the construction of self-similar fractals). We shows that H-0-convergence holds under the extra assumption that there exists a bounded sequence of extension operators for the reference holes. The general class of Jones-domains gives an example where this result applies. When this assumption fails, another approach, using the Poincare-Wirtinger inequality is presented. A corresponding class where it applies is that of John-domains, for which the Poincare-Wirtinger constant is controlled. The relationship between these two kinds of assumptions is also clarified.