Lee Wick Dark Energy

TL;DR

This paper explores Lee-Wick theory as a dark energy model, analyzing its cosmological evolution and stability, and finds that including self-interactions can match observations but introduces fine-tuning issues.

Contribution

It introduces a Lee-Wick dark energy model with higher derivative fields, analyzing its cosmological dynamics and stability, and discusses how self-interactions can improve observational consistency.

Findings

The model can produce phantom-dominated or tracking solutions depending on potential slopes.

Without self-interactions, the model cannot simultaneously match $ ext{w}_{ ext{DE}}$ and $ ext{Ω}_{ ext{DE}}$ observations.

Including self-interactions allows matching observed dark energy density but leads to stability issues and fine-tuning.

Abstract

We consider the cosmological application of Lee-Wick theory where a field has a higher derivative kinetic operators. The higher derivative term can be eliminated by introducing a set of auxiliary fields. We investigate the cosmological evolutions of these fields as a candidate of dark energy. This model has the same structure as so called ``quintom' model except the form of potentials and the sign of the slope of the potentials. This model can give the stable late time phantom dominated scaling solution ($\omega_{\DE} < -1$) or tracking attractors ($\omega_{\DE} = 0$) depending on the choice of the slopes of the potential. In order to be a viable dark energy candidate, the present energy density contrast of dark energy ($\Omega_{\DE}^{(0)}$) should be close to an observed value (0.73) at the same time. However, a simple toy model of the theory can not satisfy both $\omega_{\DE}^{(0)} \simeq -1$ and $\Omega_{\DE}^{(0)} = 0.73$. If we include the self interaction term of Lee Wick field, then we are able to produce the observed values of those quantities. However, in this case we are not be able to have the stable solutions and we need to suffer from the fine tuning of its mass.