Supersymmetric large extra dimensions are small and/or numerous - art. no.025007

Recently, a scenario has been proposed in which the gravitational scale cou ld be as low as the TeV scale, and extra dimensions could be large and dete ctable at the electroweak scale. Although supersymmetry is not a requiremen t of this scenario, it is nevertheless true that its best-motivated realiza tions arise in supersymmetric theories (such as M theory). We argue here th at supersymmetry can have robust, and in some instances fatal, implications for the expected experimental signature for TeV-scale gravity. The signatu re of the supersymmetric version of the scenario differs most dramatically from what has been considered in the literature because mass splittings wit hin the gravity supermultiplet in these models are extremely small, implyin g in particular the existence of a very light spin-one superpartner for the graviton. We compute the implications of this graviphoton, and show that i t can acquire dimension-four couplings to ordinary matter which can strongl y conflict with supernova bounds.