The scalar field associated with fluctuations in the positions of the two branes, the ``radion'', plays an important role determining the cosmology and collider phenomenology of the Randall-Sundrum solution to the hierarchy problem. It is now well known th

ξ0.010.1γ10

1

Λ [TeV]

Figure 5:Bound on γ=1/(

√s in TeV at which perturbative unitarity

is violated is indicated by the contours in this region.

and so Eq.(27)reduces to

−i M =−g 2 1−6ξ

4M 2W +t s .(29)

Again,the same result can be obtained through the Goldstone boson approximation,as shown in the Appendix.

For small ξand γ,the coefficient of the s/M 2W

term becomes (1−12ξ)γ2

and so there is no significant enhancement of the scalar contribution to the gauge boson scattering amplitude.However,if ξis proportional to 1/γ,then the coefficient may not be suppressed by γ2.For instance,suppose ξ=−ǫ/6γwith ǫ<∼1,then the coefficient becomes

ǫ2