(SUSY) Warped Brane World Effective Actions

Abstract:

I will describe two phenomenological studies of extra dimensional models, more specifically the Randall-Sundrum warped brane world. Very generically in brane world models, one expects deviations from 4d General Relativity below a critical distance, but also at large distances due to the presence of extra scalar fields. It is therefore important to study the effective gravity in these regimes. In the first part, we extend the known results by considering the most general consistent gravity action in d=5, which according to Einstein's postulates should contain a R^2 order term called the Gauss-Bonnet term. In the second part, I will describe a model of supersymmetry breaking in the SUSY Randall-Sundrum (RS) brane world. The minimal SUSY standard model contains O(100) free parameters describing the explicit breaking of global SUSY. A specific scenario of gravity-mediated SUSY breaking can predict the value of these terms as originating from a spontaneous breaking of local SUSY (supergravity), and justify otherwise arbitrary structures. We show that the 4d effective supergravity of the RS brane world may naturally lead to a "no-scale" structure where the weak scale-Planck scale hierarchy is naturally derived (and not assumed as usually in the MSSM), with the additional interest of dynamically fixing the radius of the extra dimension.