Mass spectrum & linear perturbations of ghost-free multi-spin-2 theory

Abstract Motivated by the spin-2 nature of gravity, we consider a theory of N $$ \mathcal{N} $$ interacting spin-2 fields, formulated in terms of vielbeins, which has been argued to be free of Boulware-Deser ghost instabilities. This is the only known such theory with non-trivial multi-field interac...

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Main Authors: J. Flinckman, S. F. Hassan
Format: Article
Language:English
Published: SpringerOpen 2025-02-01
Series:Journal of High Energy Physics
Subjects:
Online Access:https://doi.org/10.1007/JHEP02(2025)176
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author J. Flinckman
S. F. Hassan
author_facet J. Flinckman
S. F. Hassan
author_sort J. Flinckman
collection DOAJ
description Abstract Motivated by the spin-2 nature of gravity, we consider a theory of N $$ \mathcal{N} $$ interacting spin-2 fields, formulated in terms of vielbeins, which has been argued to be free of Boulware-Deser ghost instabilities. This is the only known such theory with non-trivial multi-field interactions. We develop an all-order expansion of the vielbein in terms of the metric and Lorentz field perturbations, enabling an expansion of the action in arbitrary backgrounds to any order. The mass matrix is then analysed around proportional vielbein solutions corresponding to vacuum Einstein spacetimes. It is shown that the theory exhibits a non-tachyonic spectrum with one massless and N $$ \mathcal{N} $$ − 1 massive spin-2 modes, regardless of the sign of the cosmological constant. While the massless mode is universal, the non-zero masses cannot generally be determined analytically, but we obtain the lower and upper bounds on each mass eigenvalue in terms of the parameters of the theory.
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spelling doaj-art-0c66990e8fa949ffb412988d49e4de622025-08-20T02:16:22ZengSpringerOpenJournal of High Energy Physics1029-84792025-02-012025212510.1007/JHEP02(2025)176Mass spectrum & linear perturbations of ghost-free multi-spin-2 theoryJ. Flinckman0S. F. Hassan1Department of Physics & The Oskar Klein Centre, Stockholm University, AlbaNova University CentreDepartment of Physics & The Oskar Klein Centre, Stockholm University, AlbaNova University CentreAbstract Motivated by the spin-2 nature of gravity, we consider a theory of N $$ \mathcal{N} $$ interacting spin-2 fields, formulated in terms of vielbeins, which has been argued to be free of Boulware-Deser ghost instabilities. This is the only known such theory with non-trivial multi-field interactions. We develop an all-order expansion of the vielbein in terms of the metric and Lorentz field perturbations, enabling an expansion of the action in arbitrary backgrounds to any order. The mass matrix is then analysed around proportional vielbein solutions corresponding to vacuum Einstein spacetimes. It is shown that the theory exhibits a non-tachyonic spectrum with one massless and N $$ \mathcal{N} $$ − 1 massive spin-2 modes, regardless of the sign of the cosmological constant. While the massless mode is universal, the non-zero masses cannot generally be determined analytically, but we obtain the lower and upper bounds on each mass eigenvalue in terms of the parameters of the theory.https://doi.org/10.1007/JHEP02(2025)176Classical Theories of GravityCosmological models
spellingShingle J. Flinckman
S. F. Hassan
Mass spectrum & linear perturbations of ghost-free multi-spin-2 theory
Journal of High Energy Physics
Classical Theories of Gravity
Cosmological models
title Mass spectrum & linear perturbations of ghost-free multi-spin-2 theory
title_full Mass spectrum & linear perturbations of ghost-free multi-spin-2 theory
title_fullStr Mass spectrum & linear perturbations of ghost-free multi-spin-2 theory
title_full_unstemmed Mass spectrum & linear perturbations of ghost-free multi-spin-2 theory
title_short Mass spectrum & linear perturbations of ghost-free multi-spin-2 theory
title_sort mass spectrum linear perturbations of ghost free multi spin 2 theory
topic Classical Theories of Gravity
Cosmological models
url https://doi.org/10.1007/JHEP02(2025)176
work_keys_str_mv AT jflinckman massspectrumlinearperturbationsofghostfreemultispin2theory
AT sfhassan massspectrumlinearperturbationsofghostfreemultispin2theory