Unwinding Inflation

TL;DR

Unwinding inflation is a string-inspired model where flux decay via brane nucleation causes a steady decrease in vacuum energy, leading to inflation with observable predictions like a scale-invariant spectrum, tensor modes, and non-Gaussianities.

Contribution

This paper introduces a novel inflationary mechanism based on flux unwinding in string theory, connecting bubble nucleation to observable cosmological signatures.

Findings

Achieves N e-folds of inflation with consistent density perturbations.

Predicts a non-decaying oscillatory component in the power spectrum.

Allows inflation without fine-tuning of string parameters.

Abstract

Higher-form flux that extends in all 3+1 dimensions of spacetime is a source of positive vacuum energy that can drive meta-stable eternal inflation. If the flux also threads compact extra dimensions, the spontaneous nucleation of a bubble of brane charged under the flux can trigger a classical cascade that steadily unwinds many units of flux, gradually decreasing the vacuum energy while inflating the bubble, until the cascade ends in the self-annihilation of the brane into radiation. With an initial number of flux quanta Q_{0} \simgeq N, this can result in N efolds of inflationary expansion while producing a scale-invariant spectrum of adiabatic density perturbations with amplitude and tilt consistent with observation. The power spectrum has an oscillatory component that does not decay away during inflation, relatively large tensor power, and interesting non-Gaussianities. Unwinding inflation fits naturally into the string landscape, and our preliminary conclusion is that consistency with observation can be attained without fine-tuning the string parameters. The initial conditions necessary for the unwinding phase are produced automatically by bubble formation, so long as the critical radius of the bubble is smaller than at least one of the compact dimensions threaded by flux.