Radion Mass is Milli-eV in the Goldberger-Wise Stabilization Mechanism

We point out a large correction to the radion kinetic term, within the GoldbergerWise radion stabilization mechanism, which has heretofore been overlooked. The radion mass is reduced by this factor, and takes the seesaw form mφ ∼ TeV/MPlanck. We find that mφ ∼ 10−3 − 10−1 eV, which can be close to the limit of sensitivity of present-day short-range gravitational force experiments. Moreover, the couplings of the radion are suppressed by the Planck scale, not the TeV scale. Such a light radion suffers from the usual cosmological moduli problems. Similar considerations may also affect other stabilization mechanisms which rely upon bulk matter fields.