On the energy of gravitational waves. (arXiv:2109.06864v1 [gr-qc])
<a href="http://arxiv.org/find/gr-qc/1/au:+Cai_R/0/1/0/all/0/1">Rong-Gen Cai</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Yang_X/0/1/0/all/0/1">Xing-Yu Yang</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Zhao_L/0/1/0/all/0/1">Long Zhao</a>

The energy of gravitational waves (GWs) is a fundamental problem in gravity
theory. The existing descriptions for the energy of GWs, such as the well-known
Isaacson energy-momentum tensor, suffer from several defects. Due to the
equivalence principle, the gravitational energy-momentum can only be defined
quasilocally, being associated with a closed spacelike 2-surface bounding a
region. We propose a new approach to derive the energy of GWs directly from the
quasilocal gravitational energy. Such an approach is natural and consistent
with the quasilocality of gravitational energy-momentum, and it is valid for
GWs with any wavelengths in any order of perturbations.

The energy of gravitational waves (GWs) is a fundamental problem in gravity
theory. The existing descriptions for the energy of GWs, such as the well-known
Isaacson energy-momentum tensor, suffer from several defects. Due to the
equivalence principle, the gravitational energy-momentum can only be defined
quasilocally, being associated with a closed spacelike 2-surface bounding a
region. We propose a new approach to derive the energy of GWs directly from the
quasilocal gravitational energy. Such an approach is natural and consistent
with the quasilocality of gravitational energy-momentum, and it is valid for
GWs with any wavelengths in any order of perturbations.

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