Weaker Gravity at Submillimetre Scales in Braneworld Models

Braneworld models typically predict gravity to grow stronger at short distances. In this paper, we consider braneworlds with two types of additional curvature couplings, a Gauss-Bonnet term in the bulk, and an Einstein-Hilbert (EH) term on the brane. In the regime where these terms are dominant over the bulk EH term, linearized gravity becomes weaker at short distances on the brane. In both models, the weakening of gravity is tied to the presence of ghosts in the graviton mass spectrum. We find that the ordinary coupling of matter to gravity is recovered at low energies/long wavelengths on the brane. We give some implications for cosmology and show its compatibility with observations. We also discuss the stability of compact stars.