On the Brane Cosmology of KK Gravitinos

TL;DR

This paper investigates the cosmological implications of Kaluza-Klein gravitinos in extra-dimensional models, concluding that their production conflicts with Big Bang Nucleosynthesis constraints under non-standard expansion scenarios.

Contribution

It demonstrates that KK gravitino production is incompatible with non-standard expansion after inflation in models with extra dimensions, challenging previous assumptions.

Findings

KK gravitino production conflicts with BBN constraints

No five-dimensional Planck mass allows safe KK gravitino production

Results apply to both flat and warped extra-dimensional models

Abstract

In this report I consider the cosmology of KK gravitinos in models with extra dimensions, in particular in connection with the known non--standard high energy regime of expansion which is associated with them. The main result is that the production of such KK modes, once one considers BBN constraints on the allowed entropy released in their decays, is not compatible with non--standard expansion after inflation: there is no five--dimensional Planck mass for which the produced KK gravitinos are safe with respect to BBN. This conclusion holds for both flat and warped models in which only gravity propagates in the full spacetime. This report is based on the work arXiv:0705.4227 [hep-ph].