The Self-Organized Criticality of Dark Matter in the Early Universe

TL;DR

This paper introduces a novel dark matter production mechanism based on self-organized criticality, leading to a relic abundance independent of initial conditions, and bridging freeze-in and freeze-out processes in the early universe.

Contribution

It proposes a new self-organized criticality mechanism for dark matter relic abundance, involving semi-annihilation and dark partner instability, with analytical results and implications for heavy dark matter.

Findings

Relic abundance is independent of initial conditions.

Analytical expression for relic abundance when dark partner is slightly heavier.

Provides a connection between freeze-in and freeze-out mechanisms.

Abstract

We propose a new mechanism for dark matter freeze-out that results in the self-organized criticality in dark matter production, wherein the final relic abundance is independent of initial inputs, in analogy to scale invariance in other realms of non-equilibrium physics. The dynamic of self-organized is triggered through a semi-annihilation process $\chi \phi \to \phi \phi$ in the premise of the instability of dark partner $\phi$, where $\chi$ is the dark matter candidate. The relic abundance can be analytically ascertained when the dark partner is slightly heavier than the dark matter, which permits a substantially heavy dark matter mass without violating unitarity bounds. We demonstrate that this process provides a bridge between the freeze-in and freeze-out mechanisms, and that the intricate dynamics of self-organized criticality can be actualized in a thermal dark sector bath.