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Large Gravitational Waves and Lyth Bound in Multi Brane Inflation

Axel Krause

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.

Large Gravitational Waves and Lyth Bound in Multi Brane Inflation

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 typically larger than the projected experimental sensitivity, . 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.

Paper Structure

This paper contains 5 sections, 28 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Scalar and Tensor Perturbations
  3. Multi M5-Brane Inflation
  4. Detectable Gravitational Waves
  5. Lyth Bound in Multi-Brane Inflation

Figures (1)

  • Figure 1: The straight inclined line displays the $r$-$n_S$ relation resulting from multi M5-brane inflation, which terminates at some finite lower value $r_{low} > 0$. It shows that $r$ is in general larger than the anticipated observational threshold $r_{exp} = 0.01$ (horizontal dashed line) and that the line goes right through the allowed central region. The parameter region inside the big (small) ellipse is allowed by WMAP3 data at 95% (66%) confidence level.