NonGaussianity of superhorizon curvature perturbations beyond delta N formalism
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If you have a question about this talk, please contact Helvi Witek.
We focus on the evolution of curvature perturbation on superhorizon scales by adopting the spatial gradient expansion and show that the nonlinear theory, called the beyond delta Nformalism as the nextleading order in the expansion. This formalism allows us to calculate the superhorizon evolution of a primordial nonGaussianity beyond the socalled delta N formalism which is equivalent to leading order in the gradient expansion.
As one application of our formalism for a single scalar field, we can deal with the time evolution in contrast to delta Nformalism, where curvature perturbations remain just constant, and nonlinear curvature perturbation follows the simple master equation whose form is similar as one in linear theory. We review our formalism and discuss some application to primordial bispectrum generated by the effect of varying sound speed.
This talk is part of the DAMTP Friday GR Seminar series.
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