A new bigravity model with exclusively positive branes

We propose a new "bigravity" model with two positive tension AdS(4) branes in AdS(5) bulk and no negative tension branes. The bounce of the "warp" fac tor mimics the effect of a negative brane and thus gives rise to an anomalo usly light graviton KK mode. This configuration satisfies the weak energy c ondition and has no ghost state. In addition, the extra polarization states of the massive graviton practically decouple and thus it does not contradi ct to Einsteinian gravity. However, the model has certain phenomenological difficulties associated with the presence of a negative cosmological consta nt on the branes. (C) 2001 Published by Elsevier Science B.V.