The Scale of Inflation in the Landscape

TL;DR

This paper investigates the frequency and characteristics of small-field inflation in the string theory landscape, finding it occurs exponentially more often than large-field inflation and typically involves high energy scales with undetectable gravitational waves.

Contribution

It provides a statistical analysis of inflation types in the landscape, highlighting the dominance of small-field inflation at high energy scales and its implications for observable gravitational waves.

Findings

Small-field inflation is exponentially more common than large-field inflation.

Most small-field inflation models operate at high energy scales near the sub-Planckian limit.

Predicted tensor-to-scalar ratio is around 10^{-3}, below current detection thresholds.

Abstract

We determine the frequency of regions of small-field inflation in the Wigner landscape as an approximation to random supergravities/type IIB flux compactifications. We show that small-field inflation occurs exponentially more often than large-field inflation The power of primordial gravitational waves from inflation is generically tied to the scale of inflation. For small-field models this is below observational reach. However, we find small-field inflation to be dominated by the highest inflationary energy scales compatible with a sub-Planckian field range. Hence, we expect a typical tensor-to-scalar ratio $r\sim {\cal O}(10^{-3})$ currently undetectable in upcoming CMB measurements.