Phantom without UV pathology

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.

19 pages. Several misprints corrected, several points clarified, several references added

References in corpus (3)

• Causality, Analyticity and an IR Obstruction to UV Completion
• Can dark energy evolve to the Phantom?
• Modified Gravitational Theory as an Alternative to Dark Energy and Dark Matter

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• Cheng-Weyl Vector Field and its Cosmological Application
• UV stable, Lorentz-violating dark energy with transient phantom era
• Inertial mechanism: dynamical mass as a source of particle creation
• Self-accelerating solutions of scalar-tensor gravity