On the Instability of the Lee-Wick Bounce

TL;DR

This paper investigates whether coupling radiation to a Lee-Wick scalar field can stabilize bouncing cosmologies, but finds that such stabilization requires unlikely fine tuning and generally results in singularities.

Contribution

It explores the effect of radiation coupling on Lee-Wick bounce models and demonstrates the instability under generic initial conditions.

Findings

Radiation coupling does not generally stabilize the bounce.

Fine tuning of initial phases is required for a successful bounce.

Most initial conditions lead to singularities instead of a bounce.

Abstract

It was recently realized that a model constructed from a Lee-Wick type scalar field theory yields, at the level of homogeneous and isotropic background cosmology, a bouncing cosmology. However, bouncing cosmologies induced by pressure-less matter are in general unstable to the addition of relativistic matter (i.e. radiation). Here we study the possibility of obtaining a bouncing cosmology if we add radiation coupled to the Lee-Wick scalar field. This coupling in principle would allow the energy to flow from radiation to matter, thus providing a drain for the radiation energy. However, we find that it takes an extremely unlikely fine tuning of the initial phases of the field configurations for a sufficient amount of radiative energy to flow into matter. For general initial conditions, the evolution leads to a singularity rather than a smooth bounce.