EFT & species scale: friends or foes?
Abstract Recently the notion that quantum gravity effects could manifest at scales much lower than the Planck scale has seen an intense Swamplandish revival. Dozens of works have explored how the so-called species scale — at which an effective description of gravity must break down — relates to Stri...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2025-05-01
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| Series: | Journal of High Energy Physics |
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| Online Access: | https://doi.org/10.1007/JHEP05(2025)212 |
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| author | Bruno Valeixo Bento João F. Melo |
| author_facet | Bruno Valeixo Bento João F. Melo |
| author_sort | Bruno Valeixo Bento |
| collection | DOAJ |
| description | Abstract Recently the notion that quantum gravity effects could manifest at scales much lower than the Planck scale has seen an intense Swamplandish revival. Dozens of works have explored how the so-called species scale — at which an effective description of gravity must break down — relates to String Theory and the Swampland conjectures. In particular, the interplay between this scale and the abundant towers of states becoming lighter in asymptotic regions of moduli spaces has proved to be key in understanding the real scale of quantum gravity. Nevertheless concerns have been raised regarding the validity of using infinite towers of states when estimating this scale within Effective Field Theory and, more precisely, the consistency of cutting the tower part way through in a framework that relies on a clear separation of scales. In this work we take an EFT point-of-view and provide a detailed perturbative derivation of the species scale by computing the 1-loop graviton propagator in the presence of many fields. Not only do we clarify the setup, assumptions and regimes of validity of the result, but more importantly apply the same methods to a particular infinite tower of states, where the different scales can be computed and contrasted. We show how each state in the tower contributes to the species scale and how the procedure of counting only “light fields” can be compatible with not cutting the tower, thereby maintaining the harmony between infinite towers and EFTs even in the context of the species scale. |
| format | Article |
| id | doaj-art-4c2414f95f0e42eb99b7ec8ecbb1ea63 |
| institution | DOAJ |
| issn | 1029-8479 |
| language | English |
| publishDate | 2025-05-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj-art-4c2414f95f0e42eb99b7ec8ecbb1ea632025-08-20T03:10:27ZengSpringerOpenJournal of High Energy Physics1029-84792025-05-012025515710.1007/JHEP05(2025)212EFT & species scale: friends or foes?Bruno Valeixo Bento0João F. Melo1Instituto de Física Teórica IFT-UAM/CSICInstituut voor Theoretische Fysica, KU LeuvenAbstract Recently the notion that quantum gravity effects could manifest at scales much lower than the Planck scale has seen an intense Swamplandish revival. Dozens of works have explored how the so-called species scale — at which an effective description of gravity must break down — relates to String Theory and the Swampland conjectures. In particular, the interplay between this scale and the abundant towers of states becoming lighter in asymptotic regions of moduli spaces has proved to be key in understanding the real scale of quantum gravity. Nevertheless concerns have been raised regarding the validity of using infinite towers of states when estimating this scale within Effective Field Theory and, more precisely, the consistency of cutting the tower part way through in a framework that relies on a clear separation of scales. In this work we take an EFT point-of-view and provide a detailed perturbative derivation of the species scale by computing the 1-loop graviton propagator in the presence of many fields. Not only do we clarify the setup, assumptions and regimes of validity of the result, but more importantly apply the same methods to a particular infinite tower of states, where the different scales can be computed and contrasted. We show how each state in the tower contributes to the species scale and how the procedure of counting only “light fields” can be compatible with not cutting the tower, thereby maintaining the harmony between infinite towers and EFTs even in the context of the species scale.https://doi.org/10.1007/JHEP05(2025)212Effective Field TheoriesClassical Theories of GravityString and Brane Phenomenology |
| spellingShingle | Bruno Valeixo Bento João F. Melo EFT & species scale: friends or foes? Journal of High Energy Physics Effective Field Theories Classical Theories of Gravity String and Brane Phenomenology |
| title | EFT & species scale: friends or foes? |
| title_full | EFT & species scale: friends or foes? |
| title_fullStr | EFT & species scale: friends or foes? |
| title_full_unstemmed | EFT & species scale: friends or foes? |
| title_short | EFT & species scale: friends or foes? |
| title_sort | eft species scale friends or foes |
| topic | Effective Field Theories Classical Theories of Gravity String and Brane Phenomenology |
| url | https://doi.org/10.1007/JHEP05(2025)212 |
| work_keys_str_mv | AT brunovaleixobento eftspeciesscalefriendsorfoes AT joaofmelo eftspeciesscalefriendsorfoes |