On Black Hole Echoes. (arXiv:1912.05584v2 [gr-qc] UPDATED)

<a href="http://arxiv.org/find/gr-qc/1/au:+DAmico_G/0/1/0/all/0/1">Guido D'Amico</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Kaloper_N/0/1/0/all/0/1">Nemanja Kaloper</a>

We consider a very simple model for gravitational wave echoes from black hole

merger ringdowns which may arise from local Lorentz symmetry violations that

modify graviton dispersion relations. If the corrections are sufficiently soft

so they do not remove the horizon, the reflection of the infalling waves which

trigger the echoes is very weak. As an example, we look at the dispersion

relation of a test scalar field corrected by roton-like operators depending

only on spatial momenta, in Gullstrand-Painlev’e coordinates. The near-horizon

regions of a black hole do become reflective, but only very weakly. The

resulting “bounces” of infalling waves can yield repetitive gravity wave

emissions but their power is very small. This implies that to see any echoes

from black holes we really need an egregious departure from either standard GR

or effective field theory, or both. One possibility to realize such strong

echoes is the recently proposed classical firewalls which replace black hole

horizons with material shells surrounding timelike singularities.

We consider a very simple model for gravitational wave echoes from black hole

merger ringdowns which may arise from local Lorentz symmetry violations that

modify graviton dispersion relations. If the corrections are sufficiently soft

so they do not remove the horizon, the reflection of the infalling waves which

trigger the echoes is very weak. As an example, we look at the dispersion

relation of a test scalar field corrected by roton-like operators depending

only on spatial momenta, in Gullstrand-Painlev’e coordinates. The near-horizon

regions of a black hole do become reflective, but only very weakly. The

resulting “bounces” of infalling waves can yield repetitive gravity wave

emissions but their power is very small. This implies that to see any echoes

from black holes we really need an egregious departure from either standard GR

or effective field theory, or both. One possibility to realize such strong

echoes is the recently proposed classical firewalls which replace black hole

horizons with material shells surrounding timelike singularities.

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