Bouncing shellworld embedded in charged AdS spacetime

Abstract: We investigate the cosmological evolution of a spherical brane within the shellworld (dark bubble) scenario embedded in a five-dimensional charged AdS bulk spacetime. For zero or small value of the brane cosmological constant, the shellworld universe has a nonsingular bouncing and cyclic nature with the bounce induced by the charge parameter of the bulk spacetime. On large value of the brane cosmological constant, the shellworld undergoes a nonsingular bounce and expands eternally. Under certain conditions, the brane bounces outside the bulk horizons, leading to a geometrical resolution of the Cauchy horizon instability present in standard braneworld models. Furthermore, analysis of linear scalar perturbations reveals that test scalar field modes remain regular and non-divergent across the bounce. Finally, we incorporate uniformly distributed long strings in the bulk and demonstrate that the bounce still persists while avoiding the horizon instability.