Crossing the cosmological constant barrier with kinetically interacting double quintessence

TL;DR

This paper explores a two-field quintessence dark energy model with kinetic interaction, demonstrating it can cross the cosmological constant barrier while remaining stable and fitting observational data.

Contribution

It introduces a kinetically interacting double quintessence model that enables crossing the $ ext{w}=-1$ barrier, ensuring stability and consistency with cosmological observations.

Findings

The model allows $ ext{w}_x$ to cross -1 at redshift 0.215-0.245.

The transition from deceleration to acceleration occurs at redshift 0.56-0.6.

The scalar potential varies smoothly and dark energy density evolves naturally.

Abstract

We examine the plausibility of crossing the cosmological constant ($\L$) barrier in a two-field quintessence model of dark energy, involving a kinetic interaction between the individual fields. Such a kinetic interaction may have its origin in the four dimensional effective two-field version of the Dirac-Born-Infeld action, that describes the motion of a D3-brane in a higher dimensional space-time. We show that this interaction term could indeed enable the dark energy equation of state parameter $\wx$ to cross the $\L$-barrier (i.e., $\wx = -1$), keeping the Hamiltonian well behaved (bounded from below), as well as satisfying the condition of stability of cosmological density perturbations, i.e., the positivity of the squares of the sound speeds corresponding to the adiabatic and entropy modes. The model is found to fit well with the latest Supernova Union data and the WMAP results. The best fit curve for $\wx$ crosses -1 at red-shift $z$ in the range $\sim 0.215 - 0.245$, whereas the transition from deceleration to acceleration takes place in the range of $z \sim 0.56 - 0.6$. The scalar potential reconstructed using the best fit model parameters is found to vary smoothly with time, while the dark energy density nearly follows the matter density at early epochs, becomes dominant in recent past, and slowly increases thereafter without giving rise to singularities in finite future.