Inflation models selected by the swampland distance conjecture with the Lyth bound

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Main Authors: Furuta, Yuma S., Hamada, Yuta, Kohri, Kazunori
Format: Preprint
Published: 2025
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author Furuta, Yuma S.
Hamada, Yuta
Kohri, Kazunori
author_facet Furuta, Yuma S.
Hamada, Yuta
Kohri, Kazunori
contents We investigate the extent to which the Swampland Conjecture can be employed to constrain large-field inflationary models from the perspective of quantum gravity consistency. In particular, we focus on the Swampland Distance Conjecture, which imposes an upper bound on the amplitude of primordial gravitational waves predicted by large-field inflation scenarios. This provides a striking contrast with the well-known Lyth bound, which yields a lower bound on the tensor-to-scalar ratio in such models. The two bounds thus play complementary roles in assessing the viability of inflationary scenarios. We demonstrate that, for certain representative large-field inflation models, the Swampland Distance Conjecture alone can impose more stringent upper limits on the tensor-toscalar ratio than current observational constraints from the cosmic microwave background. These findings highlight the utility of Swampland criteria as a theoretical discriminator among competing inflationary models, independent of empirical data.
format Preprint
id arxiv_https___arxiv_org_abs_2507_23320
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Inflation models selected by the swampland distance conjecture with the Lyth bound
Furuta, Yuma S.
Hamada, Yuta
Kohri, Kazunori
High Energy Physics - Theory
Cosmology and Nongalactic Astrophysics
High Energy Physics - Phenomenology
We investigate the extent to which the Swampland Conjecture can be employed to constrain large-field inflationary models from the perspective of quantum gravity consistency. In particular, we focus on the Swampland Distance Conjecture, which imposes an upper bound on the amplitude of primordial gravitational waves predicted by large-field inflation scenarios. This provides a striking contrast with the well-known Lyth bound, which yields a lower bound on the tensor-to-scalar ratio in such models. The two bounds thus play complementary roles in assessing the viability of inflationary scenarios. We demonstrate that, for certain representative large-field inflation models, the Swampland Distance Conjecture alone can impose more stringent upper limits on the tensor-toscalar ratio than current observational constraints from the cosmic microwave background. These findings highlight the utility of Swampland criteria as a theoretical discriminator among competing inflationary models, independent of empirical data.
title Inflation models selected by the swampland distance conjecture with the Lyth bound
topic High Energy Physics - Theory
Cosmology and Nongalactic Astrophysics
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2507.23320