Divergences in gravitational-wave emission and absorption from extreme mass ratio binaries
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Divergences in gravitational-wave emission and absorption from extreme mass ratio binaries. / Barausse, Enrico; Berti, Emanuele; Cardoso, Vitor; Hughes, Scott A.; Khanna, Gaurav.
In: Physical Review D, Vol. 104, No. 6, 064031, 13.09.2021.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Divergences in gravitational-wave emission and absorption from extreme mass ratio binaries
AU - Barausse, Enrico
AU - Berti, Emanuele
AU - Cardoso, Vitor
AU - Hughes, Scott A.
AU - Khanna, Gaurav
PY - 2021/9/13
Y1 - 2021/9/13
N2 - powerful technique to calculate gravitational radiation from binary systems involves a perturbative expansion: if the masses of the two bodies are very different, the "small" body is treated as a point particle of mass mp moving in the gravitational field generated by the large mass M, and one keeps only linear terms in the small mass ratio m(p)/M. This technique usually yields finite answers, which are often in good agreement with fully nonlinear numerical relativity results, even when extrapolated to nearly comparable mass ratios. Here we study two situations in which the point-particle approximation yields a divergent result: the instantaneous flux emitted by a small body as it orbits the light ring of a black hole, and the total energy absorbed by the horizon when a small body plunges into a black hole. By integrating the Teukolsky (or Zerilli/ Regge-Wheeler) equations in the frequency and time domains we show that both of these quantities diverge. We find that these divergences are an artifact of the point-particle idealization, and are able to interpret and regularize this behavior by introducing a finite size for the point particle. These divergences do not play a role in black-hole imaging, e.g., by the Event Horizon Telescope.
AB - powerful technique to calculate gravitational radiation from binary systems involves a perturbative expansion: if the masses of the two bodies are very different, the "small" body is treated as a point particle of mass mp moving in the gravitational field generated by the large mass M, and one keeps only linear terms in the small mass ratio m(p)/M. This technique usually yields finite answers, which are often in good agreement with fully nonlinear numerical relativity results, even when extrapolated to nearly comparable mass ratios. Here we study two situations in which the point-particle approximation yields a divergent result: the instantaneous flux emitted by a small body as it orbits the light ring of a black hole, and the total energy absorbed by the horizon when a small body plunges into a black hole. By integrating the Teukolsky (or Zerilli/ Regge-Wheeler) equations in the frequency and time domains we show that both of these quantities diverge. We find that these divergences are an artifact of the point-particle idealization, and are able to interpret and regularize this behavior by introducing a finite size for the point particle. These divergences do not play a role in black-hole imaging, e.g., by the Event Horizon Telescope.
KW - SAGITTARIUS-A-ASTERISK
KW - BLACK-HOLE
KW - RADIATION REACTION
KW - NORMAL-MODES
KW - STAR
KW - COLLAPSE
KW - ORBITS
KW - FIELD
U2 - 10.1103/PhysRevD.104.064031
DO - 10.1103/PhysRevD.104.064031
M3 - Journal article
VL - 104
JO - Physical Review D
JF - Physical Review D
SN - 2470-0010
IS - 6
M1 - 064031
ER -
ID: 298630803