Primordial Spikes from Wrapped Brane Inflation
  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.
