Hybrid Chaplygin gas and phantom divide crossing

TL;DR

This paper proposes a hybrid Chaplygin gas model as dark energy, which alleviates the coincidence problem, allows the equation of state to cross the phantom divide, and avoids future singularities with stable solutions.

Contribution

It introduces a novel hybrid Chaplygin gas model that addresses the coincidence problem and permits phantom divide crossing without leading to a big rip.

Findings

Equation of state crosses w=-1 transiently

Model has a de Sitter attractor in the future

Perturbation growth index matches observations

Abstract

Hybrid Chaplygin gas model is put forward, in which the gases play the role of dark energy. For this model the coincidence problem is greatly alleviated. The effective equation of state of the dark energy may cross the phantom divide $w=-1$. Furthermore, the crossing behaviour is decoupled from any gravity theories. In the present model, $w<-1$ is only a transient behaviour. There is a de Sitter attractor in the future infinity. Hence, the big rip singularity, which often afflicts the models with matter whose effective equation of state less than -1, is naturally disappear. There exist stable scaling solutions, both at the early universe and the late universe. We discuss the perturbation growth of this model. We find that the index is consistent with observations.