Gauge-invariant perturbations at second order in two-field inflation
Abstract
We study the second-order gauge-invariant adiabatic and isocurvature perturbations in terms of the scalar fields present during inflation, along with the related fully non-linear space gradient of these quantities. We discuss the relation with other perturbation quantities defined in the literature. We also construct the exact cubic action of the second-order perturbations (beyond any slow-roll or super-horizon approximations and including tensor perturbations), both in the uniform energy-density gauge and the flat gauge in order to settle various gauge-related issues. We thus provide the tool to calculate the exact non-Gaussianity beyond slow-roll and at any scale.
- Publication:
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Journal of Cosmology and Astroparticle Physics
- Pub Date:
- August 2012
- DOI:
- 10.1088/1475-7516/2012/08/023
- arXiv:
- arXiv:1111.5838
- Bibcode:
- 2012JCAP...08..023T
- Keywords:
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- Astrophysics - Cosmology and Extragalactic Astrophysics;
- High Energy Physics - Theory
- E-Print:
- 28 pages, no figures. v2: Added a summary subsection 4.3 with further discussion of the results. Generalized all super-horizon results of section 4 and appendix A to exact ones. Other minor textual changes and references added. Conclusions unchanged. Matches published version