Correlated parity violation in gravity and electromagnetism from five-dimensional spacetime
Abstract
Parity violation in the gravitational and electromagnetic sectors has been extensively investigated, yet the two are conventionally treated as independent phenomena. This separation, however, may be a four-dimensional prejudice. In higher-dimensional spacetime, gravity and electromagnetism may share a common geometric origin---and so, perhaps, does their parity violation. In this paper, we pursue this idea by constructing parity-violating Kaluza-Klein models in both Riemannian and teleparallel geometries. In Riemannian geometry, the simplest five-dimensional parity-violating term reduces to several complicated four-dimensional terms, including the familiar gravitational Chern-Simons term, which suffers from a ghost instability. In teleparallel geometry, however, the result is strikingly simple. The simplest five-dimensional parity-violating term reduces to only two ghost-free terms---the familiar Nieh-Yan term and the standard electromagnetic Chern-Simons term. Remarkably, the model predicts that the helicity-dependent dispersion shift for electromagnetic waves is exactly six times that for gravitational waves, Δω2 EM=6 Δω2GW, a background-independent relation. This relation offers a falsifiable test of unification through joint cosmic microwave background and gravitational wave birefringence observations.
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BibTeX
@misc{rao2026correlated,
title = {{Correlated parity violation in gravity and electromagnetism from five-dimensional spacetime}},
author = {Haomin Rao and Yunlong Zheng and Qi-Zhe Hou and Jian-Wen Ou and Changyong Zhu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.09299},
eprint = {2608.09299},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.09299},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Correlated parity violation in gravity and electromagnetism from five-dimensional spacetime
AU - Haomin Rao
AU - Yunlong Zheng
AU - Qi-Zhe Hou
AU - Jian-Wen Ou
AU - Changyong Zhu
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2608.09299
UR - https://arxiv.org/abs/2608.09299
AB - Parity violation in the gravitational and electromagnetic sectors has been extensively investigated, yet the two are conventionally treated as independent phenomena. This separation, however, may be a four-dimensional prejudice. In higher-dimensional spacetime, gravity and electromagnetism may share a common geometric origin---and so, perhaps, does their parity violation. In this paper, we pursue this idea by constructing parity-violating Kaluza-Klein models in both Riemannian and teleparallel geometries. In Riemannian geometry, the simplest five-dimensional parity-violating term reduces to several complicated four-dimensional terms, including the familiar gravitational Chern-Simons term, which suffers from a ghost instability. In teleparallel geometry, however, the result is strikingly simple. The simplest five-dimensional parity-violating term reduces to only two ghost-free terms---the familiar Nieh-Yan term and the standard electromagnetic Chern-Simons term. Remarkably, the model predicts that the helicity-dependent dispersion shift for electromagnetic waves is exactly six times that for gravitational waves, Δω^2_ EM=6 Δω^2_GW, a background-independent relation. This relation offers a falsifiable test of unification through joint cosmic microwave background and gravitational wave birefringence observations.
ER -