Beyond freeze-in: Dark Matter via inverse phase transition and gravitational wave signal

TL;DR

This paper introduces a new dark matter production mechanism linked with inverse phase transitions and gravitational wave signals, predicting observable gravitational waves from domain wall decay.

Contribution

It presents a novel dark matter production scenario via inverse phase transition coupled with gravitational wave predictions from domain wall dynamics.

Findings

Dark Matter can be produced efficiently through inverse phase transition.

Domain walls emit gravitational waves detectable by future experiments.

The gravitational wave peak frequency depends on the portal coupling.

Abstract

We propose a novel scenario of Dark Matter production naturally connected with generation of gravitational waves. Dark Matter is modelled as a real scalar, which interacts with the hot primordial plasma through a portal coupling to another scalar field. For a particular sign of the coupling, this system exhibits an inverse second order phase transition. The latter leads to an abundant Dark Matter production, even if the portal interaction is so weak that the freeze-in mechanism is inefficient. The model predicts domain wall formation in the Universe, long time before the inverse phase transition. These domain walls have a tension decreasing with time, and completely disappear at the inverse phase transition, so that the problem of overclosing the Universe is avoided. The domain wall network emits gravitational waves with characteristics defined by those of Dark Matter. In particular, the peak frequency of gravitational waves is determined by the portal coupling constant, and falls in the observable range for currently planned gravitational wave detectors.