2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/24478An extreme type II superconductor with internal insulating regions, namely cavities, is studied here. We find that the cavity-bearing superconductor has lower energy than the defect-free superconductor above a critical magnetic induction $B^*$ for insulating cavities but not for metallic ones. Using a numerical approach for the Ginzburg-Landau theory we compute and compare free energy densities for several cavity radii and at least for two cavity densities, assuming a cubic lattice of spherical cavities.7 pages, 4 figures, to be published in Europhysics LettersSuperconductivitytext