Gravitational Wave Symphony from Oscillating Spectator Scalar Fields

TL;DR

This paper explores how oscillating scalar fields in the early Universe can produce detectable stochastic gravitational wave backgrounds, potentially explaining recent pulsar timing array signals and providing dark matter or dark radiation candidates.

Contribution

It systematically analyzes scalar field models via lattice simulations, demonstrating their potential to generate observable gravitational waves and dark matter signals.

Findings

Detectable gravitational wave signals over a broad frequency range.

Potential explanation for recent pulsar timing array observations.

Models naturally produce ultralight dark matter or dark radiation.

Abstract

We investigate a generic source of stochastic gravitational wave background due to the parametric resonance of oscillating scalar fields in the early Universe. By systematically analyzing benchmark models through lattice simulations and considering a wide range of parameters, we demonstrate that such a scenario can lead to detectable signals in gravitational wave detectors over a broad frequency range and potentially address the recent findings by pulsar timing array experiments. Furthermore, these models naturally yield ultralight dark matter candidates or dark radiation detectable by cosmic microwave background observatories.