Inflation with 0 ≤ c s ≤ 1

@article{Gorji2022InflationW0,
  title={Inflation with 0 ≤ c s ≤ 1},
  author={Mohammad Ali Gorji and Hayato Motohashi and Shinji Mukohyama},
  journal={Journal of Cosmology and Astroparticle Physics},
  year={2022},
  volume={2022}
}
We investigate a novel single field inflationary scenario which allows a transition between a slow-roll k-inflation with c s of order unity and a ghost inflation with c s ≃ 0, where c s is the sound speed for the curvature perturbations. We unify the two phases smoothly by appropriately taking into account a higher derivative scordatura term, which is always there from the effective field theory point of view but which becomes important only in the c s ≃ 0 regime. The model achieves the whole… 
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