Quintom model with O($N$) symmetry

TL;DR

This paper explores a generalized quintom dark energy model with O(N) symmetry, revealing that it naturally leads to late-time acceleration with equation of state w<-1 and crossing the phantom divide, differing from simpler models.

Contribution

It introduces an O(N) symmetric quintom model with exponential potentials, showing novel late-time attractors with w<-1 and phantom divide crossing, not guaranteed in simpler models.

Findings

Universe always evolves to w<-1 attractors.

Crossing of the phantom divide occurs naturally.

Accelerating solutions are the dominant late-time attractors.

Abstract

We investigate the quintom model of dark energy in the generalized case where the corresponding canonical and phantom fields possess O($N$) symmetries. Assuming exponential potentials we find that this O$(N)$ quintom paradigm exhibits novel properties comparing to the simple canonical and phantom scenarios. In particular, we find that the universe cannot result in a quintessence-type solution with $w>-1$, even in the cases where the phantom field seems to be irrelevant. On the contrary, there are always late-time attractors which correspond to accelerating universes with $w<-1$ and with a recent crossing of the phantom divide, and for a very large area of the parameter space they are the only ones. This is in contrast with the previous simple-quintom results, where an accelerating universe is a possible late-time stable solution but it is not guaranteed.