Phantom without UV pathology

TL;DR

This paper introduces a simple model violating the weak energy condition with Lorentz-violating fields, allowing slow roll cosmology without ghosts or superluminal modes at certain scales, but with some fine-tuning.

Contribution

It demonstrates a model where weak energy condition violation occurs without ghosts or superluminal modes, enabling slow roll cosmology under specific conditions.

Findings

Weak energy condition is violated for certain field configurations.

No ghosts or superluminal modes at relevant momenta scales.

Possible slow roll cosmological regime with homogeneity and isotropy.

Abstract

We present a simple model in which the weak energy condition is violated for spatially homogeneous, slowly evolving fields. The excitations about Lorentz-violating background in Minkowski space do not contain ghosts, tachyons or superluminal modes at spatial momenta ranging from some low scale epsilon to the UV cutoff scale, while tachyons and possibly ghosts do exist at p^2 < epsilon^2. We show that in the absence of other matter, slow roll cosmological regime is possible; in this regime p+rho<0, and yet homogeneity and isotropy are not completely spoiled (at the expence of fine-tuning), since for given conformal momentum, the tachyon mode grows for short enough period of time.