Perturbative unitarity bounds on field-space curvature in de Sitter spacetime: purity vs scattering amplitude
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866912965259689984 |
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| author | Cai, Qianhang Inada, Tomoya Ishikawa, Masataka Nishii, Kanji Noumi, Toshifumi |
| author_facet | Cai, Qianhang Inada, Tomoya Ishikawa, Masataka Nishii, Kanji Noumi, Toshifumi |
| contents | We study perturbative unitarity bounds on the field-space curvature in de Sitter spacetime, using the momentum-space entanglement approach recently proposed by Duaso Pueyo, Goodhew, McCulloch, and Pajer. As an illustration, we perform a perturbative computation of the purity in two-scalar models and compare the resulting unitarity bounds with those obtained via a flat space approximation. In particular, we find that perturbative unitarity imposes an upper bound on the field-space curvature of the Hubble scale order, in addition to a bound analogous to the flat space result. This reflects the thermal nature of de Sitter spacetime. We also discuss generalizations to higher-dimensional field spaces. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_00850 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Perturbative unitarity bounds on field-space curvature in de Sitter spacetime: purity vs scattering amplitude Cai, Qianhang Inada, Tomoya Ishikawa, Masataka Nishii, Kanji Noumi, Toshifumi High Energy Physics - Theory Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology We study perturbative unitarity bounds on the field-space curvature in de Sitter spacetime, using the momentum-space entanglement approach recently proposed by Duaso Pueyo, Goodhew, McCulloch, and Pajer. As an illustration, we perform a perturbative computation of the purity in two-scalar models and compare the resulting unitarity bounds with those obtained via a flat space approximation. In particular, we find that perturbative unitarity imposes an upper bound on the field-space curvature of the Hubble scale order, in addition to a bound analogous to the flat space result. This reflects the thermal nature of de Sitter spacetime. We also discuss generalizations to higher-dimensional field spaces. |
| title | Perturbative unitarity bounds on field-space curvature in de Sitter spacetime: purity vs scattering amplitude |
| topic | High Energy Physics - Theory Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2507.00850 |