Gravitational imprints from heavy Kaluza-Klein resonances

Abstract

We systematically study the holographic phase transition of the radion field in a five-dimensional warped model which includes a scalar potential with a powerlike behavior. We consider Kaluza-Klein (KK) resonances with masses mKK at the TeV scale or beyond. The backreaction of the radion field on the gravitational metric is taken into account by using the superpotential formalism. The confinement/deconfinement first order phase transition leads to a gravitational wave stochastic background which mainly depends on the scale mKK and the number of colors, N, in the dual theory. Its power spectrum peaks at a frequency that depends on the amount of tuning required in the electroweak sector. It turns out that the present and forthcoming gravitational wave observatories can probe scenarios where the KK resonances are very heavy. Current aLIGO data already rule out vector boson KK resonances with masses in the interval mKK∼(1-10)×105 TeV. Future gravitational experiments will be sensitive to resonances with masses mKK≲105 TeV (LISA), 108 TeV (aLIGO Design) and 109 TeV (ET). Finally, we also find that the big bang nucleosynthesis bound in the frequency spectrum turns into a lower bound for the nucleation temperature as Tn≳10-4NmKK.