Tests of Gravitational-Wave Birefringence with the Gravitational-Wave Catalog. (arXiv:2109.09718v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Wang_Y/0/1/0/all/0/1">Yi-Fan Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brown_S/0/1/0/all/0/1">Stephanie M. Brown</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shao_L/0/1/0/all/0/1">Lijing Shao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhao_W/0/1/0/all/0/1">Wen Zhao</a>
The routine detection of gravitational-wave events from compact binary
coalescence has allowed precise tests of gravity in strong field, dynamical
field, and high energy regime. To date, a total of 57 gravitational-wave events
have been reported by the third Open Gravitational-wave Catalog (3-OGC). In
this work, we report the results of testing gravitational-wave birefringence
using the events from 3-OGC. Birefringence, an effect where the left- and
right-handed polarizations of gravitational waves follow different equations of
motion, occurs when the parity symmetry of gravity is broken. This arises
naturally in the effective field theory extension of general relativity. Using
Bayesian inference with state-of-the-art waveform modeling, we use all events
in 3-OGC to constrain the lower limit of energy scale at which parity violation
effects emerge. Overall we do not find evidence for a violation of general
relativity, and thus we constrain the parity-violating energy scale to
$M_mathrm{PV} > 0.14$ GeV at $90%$ confidence level, which is an improvement
over previous results by one order of magnitude. Intriguingly, we find an
outlier, GW190521, that supports the existence of birefringence over general
relativity with a higher match-filtering signal-to-noise ratio and a natural
log Bayes factor of $7.84$. Because the inferred $M_mathrm{PV}$ from GW190521
is in tension with the combined constraints, we hypothesize that this may be
caused by the limitations of the existing waveform approximants, such as
systematic errors during merger phase of the waveform, or by the existence of
physical effects such as eccentricity which are not taken into account by the
current waveform approximants.
The routine detection of gravitational-wave events from compact binary
coalescence has allowed precise tests of gravity in strong field, dynamical
field, and high energy regime. To date, a total of 57 gravitational-wave events
have been reported by the third Open Gravitational-wave Catalog (3-OGC). In
this work, we report the results of testing gravitational-wave birefringence
using the events from 3-OGC. Birefringence, an effect where the left- and
right-handed polarizations of gravitational waves follow different equations of
motion, occurs when the parity symmetry of gravity is broken. This arises
naturally in the effective field theory extension of general relativity. Using
Bayesian inference with state-of-the-art waveform modeling, we use all events
in 3-OGC to constrain the lower limit of energy scale at which parity violation
effects emerge. Overall we do not find evidence for a violation of general
relativity, and thus we constrain the parity-violating energy scale to
$M_mathrm{PV} > 0.14$ GeV at $90%$ confidence level, which is an improvement
over previous results by one order of magnitude. Intriguingly, we find an
outlier, GW190521, that supports the existence of birefringence over general
relativity with a higher match-filtering signal-to-noise ratio and a natural
log Bayes factor of $7.84$. Because the inferred $M_mathrm{PV}$ from GW190521
is in tension with the combined constraints, we hypothesize that this may be
caused by the limitations of the existing waveform approximants, such as
systematic errors during merger phase of the waveform, or by the existence of
physical effects such as eccentricity which are not taken into account by the
current waveform approximants.
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