• DOI:10.1103/PhysRevD.76.083511
• Corpus ID: 119301594

Attractor scenarios and superluminal signals in k-essence cosmology

@article{Kang2007AttractorSA,
  title={Attractor scenarios and superluminal signals in k-essence cosmology},
  author={Jin U. Kang and Vitaly Vanchurin and Sergei Winitzki},
  journal={Physical Review D},
  year={2007},
  volume={76},
  pages={083511}
}

• Jin U. Kang, V. Vanchurin, S. Winitzki
• Published 27 June 2007
• Physics
• Physical Review D

Cosmological scenarios with k-essence are invoked in order to explain the observed late-time acceleration of the Universe. These scenarios avoid the need for fine-tuned initial conditions (the 'coincidence problem') because of the attractorlike dynamics of the k-essence field {phi}. It was recently shown that all k-essence scenarios with Lagrangians p=L(X){phi}{sup -2}, where X{identical_to}(1/2){phi}{sub ,{mu}}{phi}{sup ,{mu}}, necessarily involve an epoch where perturbations of {phi} propagate faster than light (the 'no-go theorem'). We carry out a comprehensive study of attractorlike cosmological solutions ('trackers') involving a k-essence scalar field {phi} and another matter component. The result of this study is a complete classification of k-essence Lagrangians that admit asymptotically stable tracking solutions, among all Lagrangians of the form p=K({phi})L(X). Using this classification, we select the class of models that describe the late-time acceleration and avoid the coincidence problem through the tracking mechanism. An analogous 'no-go theorem' still holds for this class of models, indicating the existence of a superluminal epoch. In the context of k-essence cosmology, the superluminal epoch does not lead to causality violations. We discuss the implications of superluminal signal propagation for possible causality violations in Lorentz-invariant field theories.