I-Love-Q relations in Einstein-Aether theory

Kai Vylet, Siddarth Ajith, Kent Yagi, Nicolás Yunes

Research output: Contribution to journalArticlepeer-review

Abstract

Although Lorentz symmetry is a staple of general relativity (GR), there are several reasons to believe it may not hold in a more advanced theory of gravity, such as quantum gravity. Einstein-Aether theory is a modified theory of gravity that breaks Lorentz symmetry by introducing a dynamical vector field called the aether. The theory has four coupling constants that characterize deviations from GR and that must be determined through observations. Although three of the four parameters have been constrained by various empirical observations and stability requirements, one, called cω, remains essentially unconstrained. The aim of this work is to see if a constraint on cω can be derived from the I-Love-Q universal relations for neutron stars, which connect the neutron star moment of inertia (I), the tidal Love number (Love), and the quadrupole moment (Q) in a way that is insensitive to uncertainties in the neutron star equation-of-state. To understand if the theory can be constrained through such relations, we model slowly rotating or weakly tidally deformed neutron stars in Einstein-Aether theory, derive their I-Love-Q relations, and study how they depend on cω. We find that the I-Love-Q relations in Einstein-Aether theory are insensitive to cω and that they are close to the relations in GR. This means that the I-Love-Q relations in Einstein-Aether theory remain universal but cannot be used to constrain the theory. These results indicate that to constrain the theory with neutron stars, it is necessary to investigate relations involving other observables.

Original languageEnglish (US)
Article number024054
JournalPhysical Review D
Volume109
Issue number2
DOIs
StatePublished - Jan 15 2024
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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