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arxiv: 1308.5341 · v1 · pith:Z2N36MOYnew · submitted 2013-08-24 · 🌌 astro-ph.CO · hep-th

In-in and δ N calculations of the bispectrum from non-attractor single-field inflation

Xingang Chen , Hassan Firouzjahi , Eiichiro Komatsu , Mohammad Hossein Namjoo , Misao Sasaki This is my paper
classification 🌌 astro-ph.CO hep-th
keywords bispectrumcalculationsnon-attractorsingle-fielddeltadifferentinflationmodels
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In non-attractor single-field inflation models producing a scale-invariant power spectrum, the curvature perturbation on super-horizon scales grows as ${\cal R}\propto a^3$. 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 $\delta N$ formalism). All the results agree, giving the local-form bispectrum parameter of $f^{local}_{NL}=5(1+c_s^2)/(4c_s^2)$. This result is valid for arbitrary values of the speed of sound parameter, $c_s$, for a particular non-attractor model we consider in this paper.

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