Exponentially large extra dimensions

We show how the presence of a very light scalar with a cubic self-interaction in six dimensions can stabilize the extra dimensions at radii that are naturally exponentially large, r∼l exp[(4π)3/g2], where l is a microscopic physics scale and g is the (dimensionless) cubic coupling constant. The resulting radion mode of the metric becomes a very light degree of freedom whose mass m∼1/(Mpr2) is stable under radiative corrections. For 1/r∼10-3 eV …