Inflation with $0 \leq c_{\rm s} \leq 1$

  title={Inflation with \$0 \leq c\_\{\rm s\} \leq 1\$},
  author={Mohammad Ali Gorji and Hayato Motohashi and Shinji Mukohyama},
We investigate a novel single field inflationary scenario which allows a transition between a slow-roll k-inflation with cs of order unity and a ghost inflation with cs ' 0, where cs 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 cs ' 0 regime. The model achieves the whole range… 
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