On cosmic acceleration in models with density dependant moduli

The effective equation of state of normal matter and radiation is changed in theories where the size of the compact space depends upon the local energy density. In particular we show how the dilution of a fluid due to the expansion of the universe can be compensated by an increase of the effective coupling of that fluid to gravity in the presence of a potential which acts to reduce the size of the compact space. We estimate how much cosmic acceleration can be obtained in such a model and comment on the difficulties faced in finding an appropriate potential.