0
$\begingroup$

What do we mean by "stationary" perturbations? I know that black hole perturbations are related to gravitational waves and stationary means there should be no flow of energy. But this is vague. I am looking for a better understanding of what is the exact meaning of stationary perturbation in black hole physics. Can anyone help me with this? Thank you in advance!

$\endgroup$
2
  • 3
    $\begingroup$ Can you point to a reference where you've seen this terminology used in context? $\endgroup$
    – Andrew
    Aug 21, 2021 at 19:00
  • $\begingroup$ I came across a statement "A stationary perturbation will contain no radiation at infinity either ingoing or outgoing. The energy crossing the horizon is, therefore, zero." $\endgroup$
    – apk
    Aug 22, 2021 at 18:50

1 Answer 1

1
$\begingroup$

A stationary perturbation of a black hole is a perturbation that is independent of time (or more technically a perturbation that is invariant under the time translation (Killing) symmetry of the black hole background).

This does imply that these perturbations cannot transport energy. However, some stationary perturbations of Kerr black holes are known to transport angular momentum. This is one reason why it is better to call these "stationary" rather than "static" perturbations.

$\endgroup$
2
  • $\begingroup$ I came across a statement "A stationary perturbation will contain no radiation at infinity either ingoing or outgoing. The energy crossing the horizon is, therefore, zero." Can you please explain why this is so? $\endgroup$
    – apk
    Aug 22, 2021 at 18:49
  • $\begingroup$ That seems like a dangerously simplistic statement, as counterintuitive case of the angular momentum shows. $\endgroup$
    – TimRias
    Aug 22, 2021 at 20:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.