Kaluza-Klein relics from warped reheating

TL;DR

This paper estimates the decay rates of Kaluza-Klein relics in warped throat geometries post-inflation, finding that supersymmetry breaking is necessary for their decay to avoid cosmological issues, and deriving bounds on SUSY breaking scales.

Contribution

It provides a detailed calculation of KK relic decay rates considering warped geometries and SUSY breaking, improving understanding of relic cosmological constraints.

Findings

Decay rates are significantly larger than naive estimates.

A bound of M_{3/2} > 10^9 GeV on SUSY breaking scale is derived.

Relics must decay before nucleosynthesis to avoid cosmological problems.

Abstract

It has been suggested that after brane-antibrane inflation in a Klebanov-Strassler (KS) warped throat, metastable Kaluza-Klein (KK) excitations can be formed due to nearly-conserved angular momenta along isometric directions in the throat. If sufficiently long-lived, these relics could conflict with big bang nucleosynthesis or baryogenesis by dominating the energy density of the universe. We make a detailed estimate of the decay rate of such relics using the low energy effective action of type IIB string theory compactified on the throat geometry, with attention to powers of the warp factor. We find that it is necessary to turn on SUSY-breaking deformations of the KS background in order to ensure that the most dangerous relics will decay fast enough. The decay rate is found to be much larger than the naive guess based on the dimension of the operators which break the angular isometries of the throat. For an inflationary warp factor of order $w\sim 10^{-4}$, we obtain the bound $M_{3/2} \gsim 10^9$ GeV on the scale of SUSY breaking to avoid cosmological problems from the relics, which is satisfied in the KKLT construction assumed to stabilize the compactification. Given the requirement that the relics decay before nucleosynthesis or baryogenesis, we place bounds on the mass of the relic as a function of the warp factor in the throat for more general warped backgrounds.