The interior metric is CAdS in coordinates sec 2 ρ = 1 + r 2 and we have set the AdS scale R to 1 . The induced metrics match on the surface r = r b . This metric is not expected to be a solution to string theory , and initial data corresponding to such a geometry would certainly evolve with time . Nevertheless , any string solution containing a metastable AdS bubble will share certain features of scalar field propagation that we now study .