Bumblebee Gravity -- Lessons from Perturbation Theory
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866911457857241088 |
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| author | Nilsson, Nils A. |
| author_facet | Nilsson, Nils A. |
| contents | These proceedings summarise some recent efforts in understanding a class of vector-tensor theories known as {\it bumblebee} models, which spontaneously break local Lorentz and diffeomorphism invariance. Using cosmological perturbation theory on an FLRW background, we find that for non-minimal coupling to gravity, the theory contains a ghost mode unless degeneracy conditions are imposed, after which the model becomes a subset of generalised Proca theory, and the potential is then completely fixed by the background equations. We find a constraint on the bumblebee field from the speed of tensor modes on the order of $10^{-15}$. We go further to show that scalar perturbations do not propagate at the linear level, indicating that the theory is pathological around dynamical cosmological backgrounds, a result which is independent of the form of the potential. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_13135 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Bumblebee Gravity -- Lessons from Perturbation Theory Nilsson, Nils A. General Relativity and Quantum Cosmology High Energy Physics - Theory These proceedings summarise some recent efforts in understanding a class of vector-tensor theories known as {\it bumblebee} models, which spontaneously break local Lorentz and diffeomorphism invariance. Using cosmological perturbation theory on an FLRW background, we find that for non-minimal coupling to gravity, the theory contains a ghost mode unless degeneracy conditions are imposed, after which the model becomes a subset of generalised Proca theory, and the potential is then completely fixed by the background equations. We find a constraint on the bumblebee field from the speed of tensor modes on the order of $10^{-15}$. We go further to show that scalar perturbations do not propagate at the linear level, indicating that the theory is pathological around dynamical cosmological backgrounds, a result which is independent of the form of the potential. |
| title | Bumblebee Gravity -- Lessons from Perturbation Theory |
| topic | General Relativity and Quantum Cosmology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2510.13135 |