Mass Varying Neutrinos, Quintessence, and the Accelerating Expansion of the Universe

TL;DR

This paper investigates a model where neutrino masses vary with a scalar field, explaining the universe's acceleration and phase transitions, and linking dark energy to neutrino properties without the coincidence problem.

Contribution

It presents a minimal finite-temperature quantum field theory model of mass-varying neutrinos coupled to quintessence, analyzing phase transitions and cosmological implications.

Findings

The model predicts the current universe is below its critical temperature, leading to acceleration.

A first-order phase transition occurs at the critical point, transitioning from oscillatory to rolling dark energy.

Neutrino mass and dark energy density are linked to the potential scale M, solving the coincidence problem.

Abstract

We analyze the Mass Varying Neutrino (MaVaN) scenario. We consider a minimal model of massless Dirac fermions coupled to a scalar field, mainly in the framework of finite temperature quantum field theory. We demonstrate that the mass equation we find has non-trivial solutions only for special classes of potentials, and only within certain temperature intervals. We give most of our results for the Ratra-Peebles Dark Energy (DE) potential. The thermal (temporal) evolution of the model is analyzed. Following the time arrow, the stable, metastable and unstable phases are predicted. The model predicts that the present Universe is below its critical temperature and accelerates. At the critical point the Universe undergoes a first-order phase transition from the (meta)stable oscillatory regime to the unstable rolling regime of the DE field. This conclusion agrees with the original idea of quintessence as a force making the Universe roll towards its true vacuum with zero \Lambda-term. The present MaVaN scenario is free from the coincidence problem, since both the DE density and the neutrino mass are determined by the scale M of the potential. Choosing M ~ 10^{-3} eV to match the present DE density, we can obtain the present neutrino mass in the range m ~ 10^{-2}-1 eV and consistent estimates for other parameters of the Universe.