2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/193887We give an extensive study of the tunnelling between arbitrary (anti-)de Sitter spacetimes separated by an infinitesimally thin relativistic shell in arbitrary spacetime dimensions. In particular, we find analytically an exact expression for the tunnelling amplitude. The detailed spacetime structures that can arise are discussed, together with an effective "regularization scheme" for "before tunnelling" configurations.LaTeX, 23 pages, 20 figures: in print on Phys. Rev. D; structure of the paper streamlined, some typos corrected, one reference added, one figure added with a contourplot of the transition probability; various corrections also in the figures with the Penrose diagrams of the tunnellingGeneral Relativity and Quantum CosmologyHigh Energy Physics - Theorytext