Induced Spins from Scattering Experiments of Initially Nonspinning Black Holes. (arXiv:1909.08621v1 [gr-qc])

Induced Spins from Scattering Experiments of Initially Nonspinning Black Holes. (arXiv:1909.08621v1 [gr-qc])
<a href="http://arxiv.org/find/gr-qc/1/au:+Nelson_P/0/1/0/all/0/1">Patrick E. Nelson</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Etienne_Z/0/1/0/all/0/1">Zachariah B. Etienne</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+McWilliams_S/0/1/0/all/0/1">Sean T. McWilliams</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Nguyen_V/0/1/0/all/0/1">Viviana Nguyen</a>

When two relativistically boosted, nonspinning black holes pass by one
another on a scattering trajectory, we might expect the tidal interaction to
spin up each black hole. We present the first exploration of this effect,
appearing at fourth post-Newtonian order, with full numerical relativity
calculations. The basic set up for the calculations involves two free
parameters: the initial boost of each black hole and the initial angle between
their velocity vectors, with zero angle corresponding to a head-on trajectory.
To minimize gauge effects, we measure final spins only if the black holes reach
a final separation of at least $20M$. Fixing the initial boost, we find that as
the initial angle decreases toward the scattering/non-scattering limit, the
spin-up grows nonlinearly. In addition, as initial boosts are increased from
$0.42c$ to $0.78c$, the largest observed final dimensionless spin on each black
hole increases nonlinearly from $0.02$ to $0.20$. Based on these results, we
conclude that much higher spin-ups may be possible with larger boosts, although
achieving this will require improved numerical techniques.

When two relativistically boosted, nonspinning black holes pass by one
another on a scattering trajectory, we might expect the tidal interaction to
spin up each black hole. We present the first exploration of this effect,
appearing at fourth post-Newtonian order, with full numerical relativity
calculations. The basic set up for the calculations involves two free
parameters: the initial boost of each black hole and the initial angle between
their velocity vectors, with zero angle corresponding to a head-on trajectory.
To minimize gauge effects, we measure final spins only if the black holes reach
a final separation of at least $20M$. Fixing the initial boost, we find that as
the initial angle decreases toward the scattering/non-scattering limit, the
spin-up grows nonlinearly. In addition, as initial boosts are increased from
$0.42c$ to $0.78c$, the largest observed final dimensionless spin on each black
hole increases nonlinearly from $0.02$ to $0.20$. Based on these results, we
conclude that much higher spin-ups may be possible with larger boosts, although
achieving this will require improved numerical techniques.

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