Gravity-induced instability and gauge field localization

The spectrum of a massless bulk scalar field \Phi, with a possible interaction term of the form -\xi R \Phi^{2}, is investigated in the case of RS-geometry [1]. We show that the zero mode for \xi=0, turns into a tachyon mode, in the case of a nonzero negative value of \xi (\xi<0). As we see, the existence of the tachyon mode destabilizes the \Phi=0 vacuum, against a new stable vacuum with nonzero \Phi near the brane, and zero in the bulk. By using this result, we can construct a simple model for the gauge field localization, according to the philosophy of Dvali and Shifman (Higgs phase on the brane, confinement in the bulk).