Tensor modes on the string theory landscape

TL;DR

This paper estimates the distribution of tensor mode fractions in string theory vacua, linking inflationary mechanisms to observable cosmological parameters, and suggests regional estimates for specific compactifications.

Contribution

It provides a novel approach to estimate the distribution of tensor modes across the string theory landscape, considering eternal inflation and quantum tunneling effects.

Findings

Tensor mode fraction distribution is unbiased by inflation type.

Regional estimates for small-field vs large-field inflation are feasible.

The approach connects string theory vacua to observable cosmological parameters.

Abstract

We attempt an estimate for the distribution of the tensor mode fraction $r$ over the landscape of vacua in string theory. The dynamics of eternal inflation and quantum tunneling lead to a kind of democracy on the landscape, providing no bias towards large-field or small-field inflation regardless of the class of measure. The tensor mode fraction then follows the number frequency distributions of inflationary mechanisms of string theory over the landscape. We show that an estimate of the relative number frequencies for small-field vs large-field inflation, while unattainable on the whole landscape, may be within reach as a regional answer for warped Calabi-Yau flux compactifications of type IIB string theory.