# Mass varying neutrinos, symmetry breaking, and cosmic acceleration

## TL;DR

This paper proposes a novel model where mass-varying neutrinos trigger cosmic acceleration through symmetry breaking, resulting in a dynamical dark energy that differs from the standard cosmological constant.

## Contribution

It introduces a new mechanism linking neutrino mass variation and symmetry breaking to cosmic acceleration without relying on adiabaticity, avoiding associated instabilities.

## Key findings

- Neutrinos become nonrelativistic, breaking Z2 symmetry.
- The quintessence potential turns positive, acting like a cosmological constant.
- The model predicts a dynamical dark energy with non-persistent acceleration.

## Abstract

We introduce a new proposal for the onset of cosmic acceleration based on mass-varying neutrinos. When massive neutrinos become nonrelativistic, the $Z_2$ symmetry breaks, and the quintessence potential becomes positive from its initially zero value. This positive potential behaves like a cosmological constant at the present era and drives the Universe's acceleration during the slow roll evolution of the quintessence. In contrast to $\Lambda$CDM model, the dark energy in our model is dynamical, and the acceleration is not persistent. Contrary to some of the previous models of dark energy with mass-varying neutrinos, we do not use the adiabaticity condition which leads to instability.