Extreme-mass-ratio inspirals into rotating boson stars: nonintegrability, chaos, and transient resonances. (arXiv:2305.05691v1 [gr-qc])
<a href="http://arxiv.org/find/gr-qc/1/au:+Destounis_K/0/1/0/all/0/1">Kyriakos Destounis</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Angeloni_F/0/1/0/all/0/1">Federico Angeloni</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Vaglio_M/0/1/0/all/0/1">Massimo Vaglio</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Pani_P/0/1/0/all/0/1">Paolo Pani</a>
General relativity predicts that black holes are described by the Kerr
metric, which has integrable geodesics. This property is crucial to produce
accurate waveforms from extreme-mass-ratio inspirals. Astrophysical
environments, modifications of gravity and new fundamental fields may lead to
nonintegrable geodesics, inducing chaotic effects. We study geodesics around
self-interacting rotating boson stars and find robust evidence of
nonintegrability and chaos. We identify islands of stability around resonant
orbits, where the orbital radial and polar oscillation frequency ratios, known
as rotation numbers, remain constant throughout the island. These islands are
generically present both in the exterior and the interior of compact boson
stars. A monotonicity change of rotation curves takes place as orbits travel
from the exterior to the interior of the star. Therefore, configurations with
neutron-star-like compactness can support degenerate resonant islands. This
anomaly is reported here for the first time and it is not present in black
holes. Such configurations can also support extremely prolonged resonant
islands that span from the exterior to the interior of the star and are
shielded by thick chaotic layers. We adiabatically evolve inspirals using
approximated post-Newtonian fluxes and find time-dependent plateaus in the
rotation curves which are associated with island-crossing orbits. Crossings of
external islands give rise to typical gravitational-wave glitches found in
non-Kerr objects. Furthermore, when an inspiral is traversing an internal
island that is surrounded by a thick chaotic layer, a new type of simultaneous
multifrequency glitch occurs that may be detectable with space interferometers
such as LISA, and can serve as evidence of an extreme-mass-ratio inspiral
around a supermassive boson star.
General relativity predicts that black holes are described by the Kerr
metric, which has integrable geodesics. This property is crucial to produce
accurate waveforms from extreme-mass-ratio inspirals. Astrophysical
environments, modifications of gravity and new fundamental fields may lead to
nonintegrable geodesics, inducing chaotic effects. We study geodesics around
self-interacting rotating boson stars and find robust evidence of
nonintegrability and chaos. We identify islands of stability around resonant
orbits, where the orbital radial and polar oscillation frequency ratios, known
as rotation numbers, remain constant throughout the island. These islands are
generically present both in the exterior and the interior of compact boson
stars. A monotonicity change of rotation curves takes place as orbits travel
from the exterior to the interior of the star. Therefore, configurations with
neutron-star-like compactness can support degenerate resonant islands. This
anomaly is reported here for the first time and it is not present in black
holes. Such configurations can also support extremely prolonged resonant
islands that span from the exterior to the interior of the star and are
shielded by thick chaotic layers. We adiabatically evolve inspirals using
approximated post-Newtonian fluxes and find time-dependent plateaus in the
rotation curves which are associated with island-crossing orbits. Crossings of
external islands give rise to typical gravitational-wave glitches found in
non-Kerr objects. Furthermore, when an inspiral is traversing an internal
island that is surrounded by a thick chaotic layer, a new type of simultaneous
multifrequency glitch occurs that may be detectable with space interferometers
such as LISA, and can serve as evidence of an extreme-mass-ratio inspiral
around a supermassive boson star.
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