Extended $δN$ formalism: Nonspatially Flat Separate Universe Approach
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arXiv
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| Autori principali: | , , |
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| _version_ | 1866910984656912384 |
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| author | Artigas, Danilo Pi, Shi Tanaka, Takahiro |
| author_facet | Artigas, Danilo Pi, Shi Tanaka, Takahiro |
| contents | The $δN$ formalism is a powerful approach to compute non-linearly the large-scale evolution of the comoving curvature perturbation $ζ$. It assumes a set of FLRW patches that evolve independently, but in doing so, all the gradient terms are discarded, which are not negligibly small in models beyond slow-roll. In this Letter, we extend the formalism to capture these gradient corrections by encoding them in a homogeneous-spatial-curvature contribution assigned to each FLRW patch. For a concrete example, we apply this formalism to the ultra-slow-roll inflation, and find that it can correctly describe the large-scale evolution of the comoving curvature perturbation from the horizon exit. We also briefly discuss non-Gaussianities in this context. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2408_09964 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Extended $δN$ formalism: Nonspatially Flat Separate Universe Approach Artigas, Danilo Pi, Shi Tanaka, Takahiro Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology High Energy Physics - Theory The $δN$ formalism is a powerful approach to compute non-linearly the large-scale evolution of the comoving curvature perturbation $ζ$. It assumes a set of FLRW patches that evolve independently, but in doing so, all the gradient terms are discarded, which are not negligibly small in models beyond slow-roll. In this Letter, we extend the formalism to capture these gradient corrections by encoding them in a homogeneous-spatial-curvature contribution assigned to each FLRW patch. For a concrete example, we apply this formalism to the ultra-slow-roll inflation, and find that it can correctly describe the large-scale evolution of the comoving curvature perturbation from the horizon exit. We also briefly discuss non-Gaussianities in this context. |
| title | Extended $δN$ formalism: Nonspatially Flat Separate Universe Approach |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2408.09964 |