No ghost state of Gauss–Bonnet interaction in warped backgrounds Original Research Article

A general solution to the Einstein field equations with the Gauss–Bonnet (GB) term in an AdS5 bulk background implies that the GB coupling α can take either sign (+ or −), though a positive α will be more meaningful. By considering linearized gravity with the GB term in the Randall–Sundrum (RS) a singular 3-brane model, we study the gravitational interactions between matter sources localized on the brane. With correctly defined boundary conditions on the brane, we find a smooth behavior of graviton propagators and hence the zero-mode solution as a 4d massless graviton localized on the brane with correct momentum and tensor structures. The coupling α modifies the graviton propagators both on the brane and in the bulk. The issue on ghost state of the GB term is resolved, and we find that there is no real ghost (negative norm) state of the GB term in the RS single brane picture. The latter condition leads to a consistency in the coupling between the brane matter and the bulk gravity. We also elucidate about the possibilities for behavior of a test particle on the brane and in the bulk.