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arXiv · 1208.6011

The inflationary bispectrum with curved field-space

Joseph Elliston·David Seery·Reza Tavakol
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Abstract

We compute the covariant three-point function near horizon-crossing for a system of slowly-rolling scalar fields during an inflationary epoch, allowing for an arbitrary field-space metric. We show explicitly how to compute its subsequent evolution using a covariantized version of the separate universe or "delta-N" expansion, which must be augmented by terms measuring curvature of the field-space manifold, and give the nonlinear gauge transformation to the comoving curvature perturbation. Nonlinearities induced by the field-space curvature terms are a new and potentially significant source of non-Gaussianity. We show how inflationary models with non-minimal coupling to the spacetime Ricci scalar can be accommodated within this framework. This yields a simple toolkit allowing the bispectrum to be computed in models with non-negligible field-space curvature.

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Joseph Elliston, David Seery, Reza Tavakol. 2012-08-29. The inflationary bispectrum with curved field-space. https://doi.org/10.1088/1475-7516%2F2012%2F11%2F060

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