== BMS-invariant wave equations ==

 . Evangelos Melas
 . ''University of Athens''

The standard approach to gravitational waves produced by a
distant source assumes that the Minkowski metric is perturbed by the
incoming wave as g,,μν,, = η,,μν,, + ε h,,μν,, , with ε^2^<<ε. Replacing this in
the vacuum Einstein’s equations and using the de Donder gauge, we
obtain the well-known linear wave equation in Minkowski’s space–time.
On the other hand, since the supertranslations depend on the source’s
rotation, the asymptotically flat BMS-invariant metric also carries
informations on that rotation angle. The general expression of the
BMS-invariant metric βμν has been shown to be not invariant under the
Poincar´e group, except in the particular case when the source
collapses into a spherically symmetric system It follows that the
correct wave equation will also be invariant under the BMS group,
written with the BMS-invariant metric. Presumably this is not the wave
equation used in LIGO considerations. Therefore it is likely that some
corrections should be made. With this motivation BMS-invariant wave
equations are derived.