Primordial Spikes from Wrapped Brane Inflation

TL;DR

This paper explores how wrapped brane inflation can produce sharp, localized spikes in the curvature perturbation spectrum due to resonant excitation of Kaluza-Klein modes, offering a potential observational probe of extra dimensions.

Contribution

It demonstrates that KK mode excitations during wrapped brane inflation induce parametric resonance, creating observable spikes in the primordial perturbation spectrum.

Findings

Resonant KK mode excitation causes sharp spectral spikes.

Localized resonance effects occur in narrow wave number ranges.

Potential for cosmological observations to probe extra dimensions.

Abstract

Cosmic inflation driven by branes wrapping the extra dimensions involves Kaluza-Klein (KK) degrees of freedom in addition to the zero-mode position of the brane which plays the role of the inflaton. As the wrapped brane passes by localized sources or features along its inflationary trajectory in the extra dimensional space, the KK modes along the wrapped direction are excited and start to oscillate during inflation. We show that the oscillating KK modes induce parametric resonance for the curvature perturbations, generating sharp signals in the perturbation spectrum. The effective four dimensional picture is a theory where the inflaton couples to the heavy KK modes. The Nambu-Goto action of the brane sources couplings between the inflaton kinetic terms and the KK modes, which trigger significant resonant amplification of the curvature perturbations. We find that the strong resonant effects are localized to narrow wave number ranges, producing spikes in the perturbation spectrum. Investigation of such resonant signals opens up the possibility of probing the extra dimensional space through cosmological observations.