2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/189795In this paper we provide a short review of the main results developed in hep-th/0604086. We focus on linearised vacuum perturbations about the self-accelerating branch of solutions in the DGP model. These are shown to contain a ghost in the spectrum for any value of the brane tension. We also comment on hep-th/0607099, where some counter arguments have been presented.Minor typos correctedHigh Energy Physics - Theorytext