# Dynamical Casimir effect for gravitons in bouncing braneworlds

## TL;DR

This paper investigates the creation of gravitons in a five-dimensional braneworld scenario with bouncing branes, analyzing their spectrum, energy density, and implications for cosmology, including constraints from nucleosynthesis and dark matter considerations.

## Contribution

It provides a detailed calculation of graviton production in a bouncing braneworld, highlighting the spectrum, energy density, and the role of Kaluza-Klein modes, with implications for cosmology.

## Key findings

- Massless gravitons have a blue spectrum.
- Energy density satisfies nucleosynthesis bounds.
- Kaluza-Klein modes unlikely to be dark matter.

## Abstract

We consider a two-brane system in a five-dimensional anti-de Sitter spacetime. We study particle creation due to the motion of the physical brane which first approaches the second static brane (contraction) and then recedes from it(expansion). The spectrum and the energy density of the generated gravitons are calculated. We show that the massless gravitons have a blue spectrum and that their energy density satisfies the nucleosynthesis bound with very mild constraints on the parameters. We also show that the Kaluza-Klein modes cannot provide the dark matter in an anti-de-Sitter braneworld. However, for natural choices of parameters, backreaction from the Kaluza-Klein gravitons may well become important. The main findings of this work have been published in the form of a Letter [R. Durrer and M. Ruser, Phys. Rev. Lett. 99, 071601 (2007), arXiv:0704.0756].