Octupolar Gravitational Radiation in de Sitter Spacetime

@misc{harsh2026octupolar,
  title = {{Octupolar Gravitational Radiation in de Sitter Spacetime}},
  author = {Harsh and Omkar Shetye and Amitabh Virmani},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2608.10593},
  eprint = {2608.10593},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.10593},
}

TY  - UNPB
TI  - Octupolar Gravitational Radiation in de Sitter Spacetime
AU  - Harsh
AU  - Omkar Shetye
AU  - Amitabh Virmani
PY  - 2026
DA  - 2026/09/15
PB  - arXiv
DO  - 10.48550/arxiv.2608.10593
UR  - https://arxiv.org/abs/2608.10593
AB  - We derive the gravitational radiation generated by a localised matter source in de Sitter spacetime at octupolar order in the multipolar expansion, working in generalised harmonic gauge in the future Poincaré patch. The scalar, vector, and tensor perturbation equations are solved explicitly, taking into account the cosmological tail. This constitutes the first extension of the de Sitter multipolar expansion beyond quadrupolar order. A key technical ingredient is a universal multipole moment differentiation identity, which unifies the relations between multipole moments into a single recursive formula and enables a controlled extension to higher multipoles. Using the symmetric trace-free tensor formalism of Blanchet, Damour, and Iyer, we further develop a systematic translation of the radiative solution into a spherical harmonic basis, and apply it to both the quadrupolar and octupolar metric perturbations. This representation renders the angular structure of the radiation manifest, simplifies the verification of the linearised field equations, and facilitates direct comparison with Bondi-gauge and other perturbative treatments of de Sitter spacetime.
ER  -