Large Gravitational Waves and Lyth Bound in Multi Brane Inflation

TL;DR

This paper demonstrates that multi M5-brane inflation in heterotic M-theory predicts a detectable gravitational wave spectrum, implying high inflationary energy scales and super-Planckian field variations, with implications for theoretical modeling.

Contribution

It shows that multi M5-brane inflation can produce observable gravitational waves, addressing issues related to large field variations in inflation models.

Findings

Gravitational wave tensor fraction r exceeds 0.01 in multi M5-brane inflation.

High inflationary energy scale associated with detectable gravitational waves.

Multi-brane inflation models mitigate problems of super-Planckian field variations.

Abstract

It is shown that multi M5-brane inflation in heterotic M-theory gives rise to a detectable gravitational wave power spectrum with tensor fraction $r$ typically larger than the projected experimental sensitivity, $r_{exp} = 0.01$. A measurable gravitational wave power spectrum entails a large inflationary energy scale and a super-Planckian inflaton variation. They present serious problems for particle theory model building resp. a reliable effective field theory description. These problems are eased or even absent in multi-brane inflation models and multi M5-brane inflation, in particular.