Stochastic gravitational wave background from early dark energy

TL;DR

This paper investigates how early dark energy models can produce a stochastic gravitational wave background through scalar field fluctuations, with potential observability in the femto-Hz frequency range, constrained by CMB data.

Contribution

It demonstrates the generation of gravitational waves from early dark energy models using 3D lattice simulations, highlighting the role of tachyonic instability in specific $ ext{α}$-attractor models.

Findings

Significant gravitational wave production via tachyonic instability.

Peak of gravitational wave spectrum around femto-Hz frequency.

Constraints on models from cosmic microwave background observations.

Abstract

We study the production of stochastic gravitational wave background from early dark energy (EDE) model. It is caused by resonant amplification of scalar field fluctuations, which easily takes place for typical EDE potential based on the string axion or $\alpha$-attractor model. The resultant spectrum of gravitational wave background is computed by performing 3D lattice simulations. We show that, specifically in some class of generalized $\alpha$-attractor EDE model, a significant amount of gravitational waves can be produced via tachyonic instability with a peak around femto-Hz frequency range. Models predicting such gravitational waves can be constrained by the cosmic microwave background observations.