Abstract
The open question of whether a black hole can become tidally deformed by an external gravitational field has profound implications for fundamental physics, astrophysics, and gravitational-wave astronomy. Love tensors characterize the tidal deformability of compact objects such as astrophysical (Kerr) black holes under an external static tidal field. We prove that all Love tensors vanish identically for a Kerr black hole in the nonspinning limit or for an axisymmetric tidal perturbation. In contrast to this result, we show that Love tensors are generically nonzero for a spinning black hole. Specifically, to linear order in the Kerr black hole spin and the weak perturbing tidal field, we compute in closed form the Love tensors that couple the mass-type and current-type quadrupole moments to the electric-type and magnetic-type quadrupolar tidal fields. For a dimensionless spin , the nonvanishing quadrupolar Love tensors are , thus showing that black holes are particularly “rigid” compact objects.
- Received 2 July 2020
- Revised 18 September 2020
- Accepted 16 February 2021
DOI:https://doi.org/10.1103/PhysRevLett.126.131102
© 2021 American Physical Society
Physics Subject Headings (PhySH)
synopsis
Rising Tides on Black Holes
Published 30 March 2021
New calculations show that spinning black holes—unlike nonspinning ones—can be tidally deformed by a nonsymmetric gravitational field.
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