MHz Gravitational Waves from Short-term Anisotropic Inflation

TL;DR

This paper demonstrates that short-term anisotropic inflation is a universal phenomenon in models with exponential gauge kinetic functions, producing detectable high-frequency gravitational waves that could reveal higher-dimensional theories.

Contribution

It shows the universality of anisotropic inflation in models derived from higher-dimensional theories and predicts a distinctive gravitational wave signature in the MHz range.

Findings

Anisotropic inflation occurs universally in certain models.

Primordial gravitational waves peak at 10^{-26} to 10^{-27}.

High-frequency gravitational waves could probe higher-dimensional theories.

Abstract

We reveal the universality of short-term anisotropic inflation. As a demonstration, we study inflation with an exponential type gauge kinetic function which is ubiquitous in models obtained by dimensional reduction from higher dimensional fundamental theory. It turns out that an anisotropic inflation universally takes place in the later stage of conventional inflation. Remarkably, we find that primordial gravitational waves with a peak amplitude around $10^{-26}$ ~ $10^{-27}$ are copiously produced in high-frequency bands 10MHz~100MHz. If we could detect such gravitational waves in future, we would be able to probe higher dimensional fundamental theory.