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#### Testing GR with the Gravitational Wave Inspiral Signal GW170817

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2105.02191.pdf

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##### Citation

Shoom, A., Gupta, P. K., Krishnan, B., Nielsen, A. B., & Capano, C. (in preparation). Testing GR with the Gravitational Wave Inspiral Signal GW170817.

Cite as: https://hdl.handle.net/21.11116/0000-0008-8E1C-A

##### Abstract

Observations of gravitational waves from compact binary mergers have enabled

unique tests of general relativity in the dynamical and non-linear regimes. One

of the most important such tests are constraints on the post-Newtonian (PN)

corrections to the phase of the gravitational wave signal. The values of these

PN coefficients can be calculated within standard general relativity, and these

values are different in many alternate theories of gravity. It is clearly of

great interest to constrain these deviations based on gravitational wave

observations. In the majority of such tests which have been carried out, and

which yield by far the most stringent constraints, it is common to vary these

PN coefficients individually. While this might in principle be useful for

detecting certain deviations from standard general relativity, it is a serious

limitation. For example, we would expect alternate theories of gravity to

generically have additional parameters. The corrections to the PN coefficients

would be expected to depend on these additional non-GR parameters whence, we

expect that the various PN coefficients to be highly correlated. We present an

alternate analysis here using data from the binary neutron star coalescence

GW170817. Our analysis uses an appropriate linear combination of non-GR

parameters that represent absolute deviations from the corresponding

post-Newtonian inspiral coefficients in the TaylorF2 approximant phase. These

combinations represent uncorrelated non-GR parameters which correspond to

principal directions of their covariance matrix in the parameter subspace. Our

results illustrate good agreement with GR. In particular, the integral non-GR

phase is $\Psi_{\mbox{non-GR}} = (0.447\pm253)\times10^{-1}$ and the deviation

from GR percentile is $p^{\mbox{Dev-GR}}_{n}=25.85\%$.

unique tests of general relativity in the dynamical and non-linear regimes. One

of the most important such tests are constraints on the post-Newtonian (PN)

corrections to the phase of the gravitational wave signal. The values of these

PN coefficients can be calculated within standard general relativity, and these

values are different in many alternate theories of gravity. It is clearly of

great interest to constrain these deviations based on gravitational wave

observations. In the majority of such tests which have been carried out, and

which yield by far the most stringent constraints, it is common to vary these

PN coefficients individually. While this might in principle be useful for

detecting certain deviations from standard general relativity, it is a serious

limitation. For example, we would expect alternate theories of gravity to

generically have additional parameters. The corrections to the PN coefficients

would be expected to depend on these additional non-GR parameters whence, we

expect that the various PN coefficients to be highly correlated. We present an

alternate analysis here using data from the binary neutron star coalescence

GW170817. Our analysis uses an appropriate linear combination of non-GR

parameters that represent absolute deviations from the corresponding

post-Newtonian inspiral coefficients in the TaylorF2 approximant phase. These

combinations represent uncorrelated non-GR parameters which correspond to

principal directions of their covariance matrix in the parameter subspace. Our

results illustrate good agreement with GR. In particular, the integral non-GR

phase is $\Psi_{\mbox{non-GR}} = (0.447\pm253)\times10^{-1}$ and the deviation

from GR percentile is $p^{\mbox{Dev-GR}}_{n}=25.85\%$.