Naturalness and stability of the generalized Chaplygin gas in the seesaw cosmon scenario

TL;DR

This paper explores a unified dark sector model combining the seesaw mechanism, generalized Chaplygin gas, and cosmon dynamics, demonstrating stability and compatibility with late-time acceleration in cosmology.

Contribution

It introduces a novel framework linking the seesaw mechanism, GCG, and cosmon equations, showing their combined effects on neutrino masses and dark energy stability.

Findings

The equation of state matches that of the GCG background cosmology.

Mass variation mechanism ensures stability against linear perturbations.

Model naturally accounts for late-time cosmological acceleration.

Abstract

The seesaw mechanism is conceived on the basis that a mass scale, $\xi$, and a dimensionless scale, $s$, can be fine-tuned in order to control the dynamics of active and sterile neutrinos through cosmon-type equations of motion: the seesaw cosmon equations. This allows for sterile neutrinos to be a dark matter candidate. In this scenario, the dynamical masses and energy densities of active and sterile neutrinos can be consistently embedded into the generalized Chaplygin gas (GCG), the unified dark sector model. In addition, dark matter adiabatically coupled to dark energy allows for a natural decoupling of the (active) mass varying neutrino (MaVaN) component from the dark sector. Thus MaVaN's turn into a secondary effect. Through the scale parameters, $\xi$ and $s$, the proposed scenario allows for a convergence among three distinct frameworks: the cosmon scenario, the seesaw mechanism for mass generation and the GCG model. It is found that the equation of state of the perturbations is the very one of the GCG background cosmology so that all the results from this approach are maintained, being smoothly modified by active neutrinos. Constrained by the seesaw relations, it is shown that the mass varying mechanism is responsible for the stability against linear perturbations and is indirectly related to the late time cosmological acceleration.