Ultra slow-turn inflation
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arXiv
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| Main Authors: | , , , |
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| Format: | Preprint |
| Published: |
2026
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| _version_ | 1866910039576412160 |
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| author | Achúcarro, Ana Christodoulidis, Perseas Gong, Jinn-Ouk Iarygina, Oksana |
| author_facet | Achúcarro, Ana Christodoulidis, Perseas Gong, Jinn-Ouk Iarygina, Oksana |
| contents | In standard multi-field models, tachyonic isocurvature perturbations generally indicate the presence of an instability. We revisit the stability of some known counterexamples and show that, in a certain class of models that we call ultra slow-turn, an exponentially decreasing turn rate can shut off this potential instability. We argue that the stability of a given model can be correctly inferred by the total entropy perturbation, even if the effective mass squared of the isocurvature perturbation is negative. Several recent supergravity- or string-inspired models such as fibre inflation, SL(2,$\mathbb{Z}$) attractors and modular inflation fall into the ultra slow-turn class. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_03204 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Ultra slow-turn inflation Achúcarro, Ana Christodoulidis, Perseas Gong, Jinn-Ouk Iarygina, Oksana High Energy Physics - Theory Cosmology and Nongalactic Astrophysics In standard multi-field models, tachyonic isocurvature perturbations generally indicate the presence of an instability. We revisit the stability of some known counterexamples and show that, in a certain class of models that we call ultra slow-turn, an exponentially decreasing turn rate can shut off this potential instability. We argue that the stability of a given model can be correctly inferred by the total entropy perturbation, even if the effective mass squared of the isocurvature perturbation is negative. Several recent supergravity- or string-inspired models such as fibre inflation, SL(2,$\mathbb{Z}$) attractors and modular inflation fall into the ultra slow-turn class. |
| title | Ultra slow-turn inflation |
| topic | High Energy Physics - Theory Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2603.03204 |