Journal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
Volume -, Issue 8, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/1475-7516/2012/08/005
Keywords
inflation; string theory and cosmology; physics of the early universe; cosmological perturbation theory
Funding
- STFC [ST/H005498/1]
- [ST/H002774/1]
- Science and Technology Facilities Council [ST/F007531/1, ST/H005498/1, ST/H002774/1] Funding Source: researchfish
- STFC [ST/H005498/1, ST/F007531/1, ST/H002774/1] Funding Source: UKRI
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We study the effect of non-trivial sound speeds on local-type non-Gaussianity during multiple-field inflation. to this end, we consider a multiple-DBI model and use the delta N 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 at 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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