Existence and uniqueness of solutions to a concentrated capacity problem with change of phase

A concentrated capacity problem posed for the heat equation in a multidimensional domain is considered. In the concentrated capacity (i.e., in a portion of the boundary of the domain) a change of phase takes place, and a Stefan-like problem is posed. This scheme has been introduced in the literature as the formal limiting case of a certain class of diffusion problems. Our main result is a theorem of continuous dependence of the solution on the data, used also to prove existence of the solution (in a weak sense), assuming only integrability of the data. The solution is found as the limit of the solutions of the approximating problems.