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Paper IPM / Astronomy / 13671  


Abstract:  
In nonattractor singlefield inflation models producing a scaleinvariant power spectrum, the curvature perturbation on superhorizon scales grows as a3. This is so far the only known class of selfconsistent singlefield models with a BunchDavies initial state that can produce a large squeezedlimit 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 Î´N formalism). All the results agree, giving the localform 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 nonattractor model we consider in this paper.
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