Cosmological Stasis from Field-Dependent Decay

TL;DR

This paper introduces a novel mechanism for cosmological stasis, where the energy composition of the universe remains constant during expansion, driven by a single particle decay regulated by a scalar field, expanding understanding of cosmic evolution.

Contribution

It demonstrates that cosmological stasis can arise from a single particle decay with a field-dependent decay width, broadening the scenarios where stasis naturally occurs in cosmology.

Findings

Stasis can be a global attractor in the universe's evolution.

Stasis solutions can be stable nodes or spirals with oscillations.

The paper provides an explicit model and discusses phenomenological constraints.

Abstract

Cosmological stasis is a new type of epoch in the cosmological timeline during which the cosmological abundances of different energy components -- such as vacuum energy, matter, and radiation -- remain constant despite the expansion of the universe. Previous studies have shown that stasis naturally arises in various scenarios beyond the Standard Model, either through sequential decays of states in large towers or via the annihilation of a single particle species in thermal equilibrium with itself. In this work, we demonstrate that stasis can also emerge from the decay of a single particle species whose decay width is dynamically regulated by a scalar field rolling down a Hubble-mass potential. By analyzing the fixed points of the dynamical system, we identify regions of the parameter space where stasis occurs as a global attractor of cosmic evolution. We also find that, depending on the specific abundance configuration, stasis solutions can manifest as either a stable node with asymptotic behavior or a stable spiral exhibiting intrinsic oscillations. Furthermore, we present an explicit model for this realization of stasis and explore its phenomenological constraints and implications.