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arXiv · 1805.09189

The observed galaxy bispectrum from single-field inflation in the squeezed limit

Kazuya Koyama·Obinna Umeh·Roy Maartens·Daniele Bertacca
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Abstract

Using the consistency relation in Fourier space, we derive the observed galaxy bispectrum from single-field inflation in the squeezed limit, in which one of the three modes has a wavelength much longer than the other two. This provides a non-trivial check of the full computation of the bispectrum based on second-order cosmological perturbation theory in this limit. We show that gauge modes need to be carefully removed in the second-order cosmological perturbations in order to calculate the observed galaxy bispectrum in the squeezed limit. We then give an estimate of the effective non-Gaussianity due to general relativistic lightcone effects that could mimic a primordial non-Gaussian signal.

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Kazuya Koyama, Obinna Umeh, Roy Maartens, Daniele Bertacca. 2018-05-23. The observed galaxy bispectrum from single-field inflation in the squeezed limit. https://doi.org/10.1088/1475-7516%2F2018%2F07%2F050

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