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arXiv · 1308.5341

In-in and $δN$ calculations of the bispectrum from non-attractor single-field inflation

Xingang Chen·Hassan Firouzjahi·Eiichiro Komatsu·Mohammad Hossein Namjoo·Misao Sasaki
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Abstract

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 $δN$ 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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Xingang Chen, Hassan Firouzjahi, Eiichiro Komatsu, Mohammad Hossein Namjoo, Misao Sasaki. 2013-08-24. In-in and $δN$ calculations of the bispectrum from non-attractor single-field inflation. https://doi.org/10.1088/1475-7516%2F2013%2F12%2F039

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