Phenomenology, astrophysics, and cosmology of theories with submillimeter dimensions and TeV scale quantum gravity - art. no. 086004

We recently proposed a solution to the hierarchy problem not relying on low -energy supersymmetry or technicolor. Instead, the problem is nullified by bringing quantum gravity down to the TeV scale. This is accomplished by the presence of n greater than or equal to 2 new dimensions of submillimeter s ize, with the SM fields localized on a 3-brane in the higher dimensional sp ace. In this paper we systematically study the experimental viability of th is scenario. Constraints arise both from strong quantum gravitational effec ts at the TeV scale, and more importantly from the production of massless h igher dimensional gravitons with TeV suppressed couplings. Theories with n> 2 are safe due mainly to the infrared softness of higher dimensional gravit y. For n = 2, the six dimensional Planck scale must be pushed above similar to 30 TeV to avoid cooling SN 1987A and distortions of the diffuse photon background. Nevertheless, the particular implementation of our framework wi thin type I string theory can evade all constraints, for any n greater than or equal to 2, with string scale m(s)similar to 1 TeV. We also explore nov el phenomena resulting from the existence of new states propagating in the higher dimensional space. The Peccei-Quinn solution to the strong CP proble m is revived with a weak scale axion in the bulk. Gauge fields in the bulk can mediate repulsive forces similar to 10(6)-10(8) times stronger than gra vity at submillimeter distances, as well as help stabilize the proton. High er-dimensional gravitons produced on our brane and captured on a different "fat" brane can provide a natural dark matter candidate. [S0556-2821(98)022 24-3].