2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49973It has recently been proposed that our universe is a three-brane embedded in a higher dimensional spacetime. Here I show that black holes on the brane, black strings intersecting the brane, and gravitational waves propagating in the bulk induce an effective energy-momentum tensor on the brane that contains negative energy densities.6 pages, LaTexHigh Energy Physics - TheoryGeneral Relativity and Quantum Cosmologytext