Constraining early dark energy with gravitational waves before recombination

TL;DR

This paper investigates how the decay of ultralight scalars into gauge bosons, proposed to resolve the Hubble tension, generates gravitational waves that are constrained by the CMB, offering a new way to test early dark energy models.

Contribution

It provides the first detailed nonlinear simulation of gravitational wave production from early dark energy decay, showing these signals exceed current observational constraints.

Findings

Gravitational wave signals surpass observational limits across parameter space.

Decay of early dark energy produces detectable gravitational waves.

Gravitational waves offer a new probe for early dark energy models.

Abstract

We show that the nonperturbative decay of ultralight scalars into Abelian gauge bosons, recently proposed as a possible solution to the Hubble tension, produces a stochastic background of gravitational waves which is constrained by the cosmic microwave background. We simulate the full nonlinear dynamics of resonant dark photon production and the associated gravitational wave production, finding the signals to exceed constraints for the entire parameter space we consider. Our findings suggest that gravitational wave production from the decay of early dark energy may provide a unique probe of these models.