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arXiv · 1203.6625

Local non-Gaussianity from rapidly varying sound speeds

Jon Emery·Gianmassimo Tasinato·David Wands
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Abstract

We study the effect of non-trivial sound speeds on local-type non-Gaussianity during multiple-field inflation. To this end, we consider a model of multiple-field DBI and use the deltaN formalism to track the super-horizon evolution of perturbations. By adopting a sum separable Hubble parameter we derive analytic expressions for the relevant quantities in the two-field case, valid beyond slow variation. We find that non-trivial sound speeds can, in principle, curve the trajectory in such a way that significant local-type non-Gaussianity is produced. Deviations from slow variation, such as rapidly varying sound speeds, enhance this effect. To illustrate our results we consider two-field inflation in the tip regions of two warped throats and find large local-type non-Gaussianity produced towards the end of the inflationary process.

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Jon Emery, Gianmassimo Tasinato, David Wands. 2012-07-16. Local non-Gaussianity from rapidly varying sound speeds. https://doi.org/10.1088/1475-7516%2F2012%2F08%2F005

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