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Paper   IPM / Astronomy / 13671
School of Astronomy
  Title:   In-in and δN calculations of the bispectrum from non-attractor single-field inflation
1.  X. Chen
2.  H. Firouzjahi
3.  Eiichiro. Komatsu
4.  M.H. Namjoo
5.  M. Sasaki
  Status:   Published
  Journal: JCAP
  Year:  2013
  Supported by:  IPM
In non-attractor single-field inflation models producing a scale-invariant power spectrum, the curvature perturbation on super-horizon scales grows as a3. This is so far the only known class of self-consistent single-field models with a Bunch-Davies initial state that can produce a large squeezed-limit bispectrum violating Maldacena's consistency relation. Given the importance of this result, we calculate the bispectrum with three different methods: using quantum field theory calculations in two different gauges, and classical calculations (the δN formalism). All the results agree, giving the local-form bispectrum parameter of flocalNL= 5(1+cs2)/(4cs2). This result is valid for arbitrary values of the speed of sound parameter, cs, for a particular non-attractor model we consider in this paper.

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