Perturbative approach for mass varying neutrinos coupled to the dark sector in the generalized Chaplygin gas scenario

TL;DR

This paper introduces a perturbative framework for studying mass-varying neutrinos coupled to dark energy models, specifically within the generalized Chaplygin gas scenario, ensuring model stability and consistency with cosmological constraints.

Contribution

It develops a novel perturbative method for analyzing MaVaN's coupled to dark sectors, applied to the GCG model, and demonstrates conditions for stability and positive sound speed.

Findings

Perturbative approach constrains coupling coefficients based on energy ratios.

GCG parameters aligned with cosmological data yield positive neutrino-scalar fluid sound speed.

Model stability depends on the universe's equation of state parameters.

Abstract

We suggest a perturbative approach for generic choices for the universe equation of state and introduce a novel framework for studying mass varying neutrinos (MaVaN's) coupled to the dark sector. For concreteness, we examine the coupling between neutrinos and the underlying scalar field associated with the generalized Chaplygin gas (GCG), a unification model for dark energy and dark matter. It is shown that the application of a perturbative approach to MaVaN mechanisms translates into a constraint on the coefficient of a linear perturbation, which depends on the ratio between a neutrino energy dependent term and scalar field potential terms. We quantify the effects on the MaVaN sector by considering neutrino masses generated by the seesaw mechanism. After setting the GCG parameters in agreement with general cosmological constraints, we find that the squared speed of sound in the neutrino-scalar GCG fluid is naturally positive. In this scenario, the model stability depends on previously set up parameters associated with the equation of state of the universe. Our results suggest that the GCG is a particularly suitable candidate for constructing a stable MaVaN scenario.