Speaker
Description
Compact extra dimensions appear in various scenarios beyond the Standard Model (SM) of physics, including string theory, but their experimental signatures have not been observed yet. If the energy scale associated with extra dimensions is too high, then the signatures will not be observable in terrestrial colliders. The cosmological period of inflation, however, is an epoch where the energies are high enough for extra-dimensional signatures to be relevant. For example, the production of on-shell Kaluza-Klein (KK) gravitons and radions during inflation could give rise to three-point functions (bispectrum) of density perturbations within the cosmological collider (CC) scenario. We compute the full shape of the bispectrum mediated by the KK gravitons and the radion for the first time, utilizing the Randall-Sundrum model. We then search for the bispectra shapes in the Planck 2018 data. We also comment on the overlap of our results with those of a generic massive spin-2 particle in the usual effective field theory of inflation, as well as comment on the usage of the cosmological bootstrap technique.