Browsing by Author "Koyama, Kazuya"

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    The observed galaxy bispectrum from single-field inflation in the squeezed limit
    (IOP Publishing, 2018) Koyama, Kazuya; Umeh, Obinna; Maartens, Roy; Bertacca, Daniele
    Using the consistency relation in Fourier space, we derive the observed galaxy bispectrum from single- eld in ation 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 e ective non- Gaussianity due to general-relativistic lightcone e ects that could mimic a primordial non-Gaussian signal.