Warped brane worlds in six dimensional supergravity

We present warped compactification solutions of six-dimensional supergravity,which are generalizations of the Randall-Sundrum warped brane world tocodimension two and to a supersymmetric context. In these solutions the dilatonvaries over the extra dimensions, and this makes the electroweak hierarchy onlypower-law sensitive to the proper radius of the extra dimensions (as opposed tobeing exponentially sensitive as in the RS model). Warping changes thephenomenology of these models because the Kaluza-Klein gap can be much largerthan the internal space's inverse proper radius. We provide examples both forRomans' nonchiral supergravity and Salam-Sezgin chiral supergravity, and inboth cases the solutions break all of the supersymmetries of the models. Weinterpret the solution as describing the fields sourced by a 3-brane and aboundary 4-brane (Romans' supergravity) or by one or two 3-branes (Salam-Sezginsupergravity), and we identify the topological constraints which are requiredby this interpretation. For both types of solutions the 3-branes are flat forall topologically-allowed values of the brane tensions. We identify the generalmechanism for and limitations of the self-tuning of the effective 4Dcosmological constant in higher-dimensional supergravity which these modelsillustrate.Comment: 47 pages, 2 figures; added reference