Linear Cosmological Perturbations in D-brane Gases

We consider linear cosmological perturbations on the background of a D-brane gas in which the compact dimensions and the dilaton are stabilized. We focus on long wavelength fluctuations and find that there are no instabilities. In particular, the perturbation of the internal space performs damped oscillations and decays in time. Therefore, the stabilization mechanism based on D-brane gases in string theory remains valid in the presence of linearized inhomogeneities.