D=5 M-theory radion supermultiplet dynamics

TL;DR

This paper derives the dynamics of the radion supermultiplet in a 4D N=1 supergravity context from 5D M-theory, exploring its geometric structure, brane solutions, and implications for cosmology.

Contribution

It presents a consistent reduction from 5D M-theory to 4D supergravity, revealing the radion's nonlinear sigma model structure and its potential cosmological applications.

Findings

Radion and pseudoscalar form an SL(2,R)/U(1) sigma model

Existence of a supersymmetric string brane solution

Radion mode has a minimum length, potentially avoiding singularities

Abstract

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 leads to an SL(2,Z) identification of the sigma model target space. The resulting radion mode has a minimum length; 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.