Bulk Gauge Fields in the Bigravity Model

Motivated by a recently proposed "bigravity" model with two positive tension $AdS_4$ branes in $AdS_5$ by Kogan et al.[hep-th/0011141], we study behavior of bulk gauge field in the model. In this case, the zero mode of the gauge field is not constant but depends on the fifth dimensional coordinate transverse to the brane. The zero mode then becomes massive on the brane. From the physical requirement that the mass must be small, a parameter of the model is constrained. We also discuss the Kaluza-Klein modes.