Curvaton Scenario in the Presence of Two Dilatons Coupled to the Scalar Curvature

The possibility of the realization of a curvaton scenario is studied in a theory in which two dilatons are introduced along with coupling to the scalar curvature. It is shown that when the two dilatons have an approximate O(2) symmetric coupling, a scalar field playing the role of the curvaton may exist in the framework of this theory without introducing any other scalar field for the curvaton. Thus the curvaton scenario can be realized, and in the simple version of the curvaton scenario, in which the curvaton potential is quadratic, the curvature perturbation with a sufficient amplitude and a nearly scale-invariant spectrum suggested by observations obtained from WMAP can be generated.