Tachyon with an inverse power-law potential in a braneworld cosmology

Abstract: We study a tachyon cosmological model based on the dynamics of a 3-brane in the bulk of the second Randall-Sundrum model extended to more general warp functions. A well known prototype of such a generalization is the bulk with a selfinteracting scalar field. As a consequence of a generalized bulk geometry the cosmology on the observer brane is modified by the scale dependent four-dimensional gravitational constant. In particular we study a power law warp factor which generates an inverse power-law potential $V\propto \varphi^{-n}$ of the tachyon field $\varphi$. We find a critical power $n_{\rm cr}$ that divides two subclasses with distinct asymptotic behaviors: a dust universe for $n>n_{\rm cr}$ and a quasi de Sitter universe for $0<n<n_{\rm cr}$.