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Polarizations of Gravitational Waves in the Bumblebee Gravity Model

7 Pith papers cite this work. Polarity classification is still indexing.

7 Pith papers citing it
abstract

Lorentz violation modifies the dispersion relation of gravitational waves (GWs), and induces birefringence and anisotropy in propagation. Our study shows that Lorentz violation can also activate multiple polarizations of GWs. We use the gauge invariants to investigate the polarizations of GWs in the bumblebee gravity model, and obtain the following results. (i) For a vector background $b^\mu$ with only a nonzero temporal component $b^t$, there are five independent propagating degrees of freedom (DOFs), which is simlar to the Einstein-aether theory. (ii) The presence of a spatial component in the background defines a preferred spatial direction which breaks rotational symmetry. We denote $\hat{\bf b}$ as the direction of the spatial part of the background and $b_s$ as its length. If GWs propagate along $\hat{\bf b}$, the polarization content is similar to the purely timelike case. (iii) If the propagation direction of GWs is separated by an angle $\beta$ to $\hat{\bf b}$, and $\beta=\arccos(b^t/b_s)$, there are only two tensor polarizations. (iv) If $\beta\neq \arccos(b^t/b_s)$, there are only two independent DOFs, and the vector and scalar modes degenerate with the tensor modes. The tensor perturbations can activate a mixture of all six polarizations simultaneously. Finally, we point out the difference in GWs between the bumblebee gravity model and the minimal Standard-Model Extension framework in the linearized regime. Current observations have placed stringent constraints on the anisotropy induced by the background, while our theoretical study still reveals some novel phenomena and provides more understanding about the interaction between the Lorentz-violating vector field and gravity.

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gr-qc 7

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2026 5 2025 2

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representative citing papers

Dynamic Aspects of Bumblebee Gravity: Post-Newtonian Approach

gr-qc · 2026-05-17 · unverdicted · novelty 5.0

Bumblebee gravity is self-consistent in PPN up to 1.5PN order only for λ = −ξ/2, producing non-zero α1, α2, a logarithmic U_B potential, and a pulsar-timing bound |ℓ| ≲ 1.6×10^{-9}.

The Science of the Einstein Telescope

gr-qc · 2025-03-15 · unverdicted · novelty 3.0

The paper provides state-of-the-art predictions for the Einstein Telescope's impact on fundamental physics, cosmology, compact-object astrophysics, and multi-messenger astronomy across its proposed configurations.

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