Gravitational Wave Spectrum from the Production of Dark Matter via the freeze-in Mechanism

TL;DR

This paper investigates the gravitational wave signals produced during the freeze-in production of dark matter in the early universe, highlighting their unique features and potential for future detection despite current technological limitations.

Contribution

It calculates the gravitational wave spectra from freeze-in dark matter production, revealing distinct spectral features for different scenarios and discussing future detection prospects.

Findings

Spectra exhibit distinct characteristics for different freeze-in scenarios.

Current detectors are insufficient to observe these gravitational waves.

Future high-frequency gravitational wave detectors could indirectly probe ultraviolet freeze-in.

Abstract

Since the first detection of gravitational waves by ground-based interferometers, it has emerged as a novel probe for exploring physics in the early universe. The particle nature of cold dark matter (DM) and its underlying production mechanisms remain long-standing unresolved issues in the field. Notably, if DM is generated through the freeze-in mechanism in the early universe, direct laboratory detection becomes extraordinarily challenging due to its extremely weak coupling with standard model particles. In this study, we calculate the graviton bremsstrahlung process involved in the freeze-in production of dark matter, deriving the gravitational wave spectra for both the conventional freeze-in mechanism and ultraviolet freeze-in scenarios. Our analysis reveals that these spectra exhibit distinct characteristics, though they fall beyond the detection limits of currently proposed gravitational wave experiments. However, advancements in high-frequency gravitational wave detection technologies in the future may offer a means to indirectly probe the ultraviolet freeze-in mechanism.