Buchdahl bound, photon ring, ISCO and radial acceleration in Einstein-æther theory - Archive ouverte HAL
Pré-Publication, Document De Travail Année : 2024

Buchdahl bound, photon ring, ISCO and radial acceleration in Einstein-æther theory

Yi-Hsiung Hsu
  • Fonction : Auteur
Anthony Lasenby
  • Fonction : Auteur
Will Barker
  • Fonction : Auteur
Michael Hobson
  • Fonction : Auteur

Résumé

Spherically symmetric Einstein-æther (EÆ) theory with a Maxwell-like kinetic term is revisited. We consider a general choice of the metric and the æther field, finding that:~(i) there is a gauge freedom allowing one always to use a diagonal metric; and~(ii) the nature of the Maxwell equation forces the æther field to be time-like in the coordinate basis. We derive the vacuum solution and confirm that the innermost stable circular orbit (ISCO) and photon ring are enlarged relative to general relativity (GR). Buchdahl's theorem in EÆ theory is derived. For a uniform physical density, we find that the upper bound on compactness is always lower than in GR. Additionally, we observe that the Newtonian and EÆ radial acceleration relations run parallel in the low pressure limit. Our analysis of EÆ theory may offer novel insights into its interesting phenomenological generalization: Æther--scalar--tensor theory (ÆST).

Dates et versions

hal-04781029 , version 1 (13-11-2024)

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Yi-Hsiung Hsu, Anthony Lasenby, Will Barker, Amel Durakovic, Michael Hobson. Buchdahl bound, photon ring, ISCO and radial acceleration in Einstein-æther theory. 2024. ⟨hal-04781029⟩
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