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 factor mimics the effect of a negative brane and thus gives rise to an anomalously light graviton KK mode. This configuration satisfies the weak energy condition and has no ghost state. In addition, the extra polarization states of the massive graviton practically decouple and thus it does not contradict to Einsteinian gravity. However, the model has certain phenomenological difficulties associated with the presence of a negative cosmological constant on the branes. (C) 2001 Published by Elsevier Science B.V.