Crossing w = −1 in Gauss–Bonnet Brane Worldwith Induced Gravity**The project supported in part bythe National Natural Science Foundation of China under Grant Nos. 10325525and 90403029, and by ``973" Project of the Ministryof Science and Technology of China under Grant No. TG1999075401

Abstract

Recent type Ia supernovas data seemingly favor a dark energy modelwhose equation of state w(z) crosses −1 very recently, whichis a much more amazing problem than the acceleration of theuniverse. In this paper we show that it is possible to realizesuch a crossing without introducing any phantom component in aGauss–Bonnet brane world with induced gravity, where afour-dimensional curvature scalar on the brane and a five-dimensionalGauss–Bonnet term in the bulk are present. In this realization,the Gauss–Bonnet term and the mass parameter in the bulk play acrucial role.