Accelerated expansion and the Goldstone ghost

TL;DR

This paper explores how a Goldstone ghost from Lorentz symmetry breaking in a hidden sector can cause a dynamic dark energy equation of state, evolving from w=-1.5 to -1 over cosmic time.

Contribution

It introduces a model where a Goldstone ghost induces a variable dark energy equation of state, linking Lorentz symmetry breaking to cosmological acceleration.

Findings

Dark energy w parameter evolves from -1.5 to -1 over time.

Lorentz symmetry breaking scale is below approximately 10 KeV.

Produced particles are mainly neutrinos.

Abstract

A vacuum instability due to a massless ghost in a hidden sector can lead to an effective equation of state for dark energy that changes smoothly from $w=-3/2$ at large redshifts, to $w\approx-1.2$ today, to $w=-1$ in the future. We discuss how this ghost can be the Goldstone boson of Lorentz symmetry breaking, and we find that this breaking in the hidden sector should occur at a scale below $\sim$10 KeV. The normal particles that are produced along with the ghosts are then predominantly neutrinos.