Title: "Stability of homogeneous extra dimensions"

In order not to be in conflict with observations it is crucial that extra dimensions (ED), if existent, are stable. It is shown that in the context of homogeneous ED, this can easily be achieved during both (4D) radiation and vacuum energy dominated eras of the cosmological evolution. During matter domination, however, there is no such possibility even for a very general class of stabilization mechanisms. It is furthermore argued that one generically expects time varying extra dimensions during any transition period such as from radiation to matter domination, even for the (assumed) case of stable ED during the latter. For more details see astro-ph/0308498.