D=5 M-theory radion supermultiplet dynamics Original Research Article

We show how the bosonic sector of the radion supermultiplet plus d=4, N=1 supergravity emerge from a consistent braneworld Kaluza–Klein reduction of D=5 M-theory. The radion and its associated pseudoscalar form an SL(2,R)/U(1) nonlinear sigma model. This braneworld system admits its own brane solution in the form of a 2-supercharge supersymmetric string. Requiring this to be free of singularities suggests an SL(2,Z) identification of the sigma model target space. The radion mode then gives a minimum length between branes; we suggest that this could be used to avoid the occurrence of singularities in brane–brane collisions. We discuss possible supersymmetric potentials for the radion supermultiplet and their relation to cosmological models such as the cyclic universe or hybrid inflation.