Brane Annihilations during Inflation

TL;DR

This paper analyzes how brane collisions during inflation affect the primordial power spectrum, revealing oscillatory features and spectral tilts that could inform cosmological observations.

Contribution

It provides an analytical study of observable signatures from brane annihilations during inflation, including effects on the power spectrum and perturbation matching conditions.

Findings

Oscillatory modulation of the power spectrum within the horizon

Reddening of the spectrum on super-horizon scales

Impact of brane collision on curvature perturbations

Abstract

We investigate brane inflation driven by two stacks of mobile branes in a throat. The stack closest to the bottom of the throat annihilates first with antibranes, resulting in particle production and a change of the equation of state parameter w. We calculate analytically some observable signatures of the collision; related decays are common in multi-field inflation, providing the motivation for this case study. The discontinuity in w enters the matching conditions relating perturbations in the remaining degree of freedom before and after the collision, affecting the power-spectrum of curvature perturbations. We find an oscillatory modulation of the power-spectrum for scales within the horizon at the time of the collision, and a slightly redder spectrum on super-horizon scales. We comment on implications for staggered inflation.