Gravitational Waves-Longitudinal or transverse

[binbagsss]

Hi,

So the gravitational waves detected by LIGO recently were transverse right?

And this is because the weak field approximation which reduces EFE to linearized holds very well at such distances and these describe that the gravtiational waves will be transverse.

I've read that you also get longitudinal components predicted by the non-linearized EFE equations- although these don't actually propagate? Do longitudinal components exist that propagate, and what would be the source?

My question is what are sources of longitudinal waves and what transverse?

So, e.g, the black-hole merger locally would be described by the non-linearized EFE as a pose to the linear, and so longitudinal components would be non-negligible near the merger? Would all sources of graviational waves have both longitudinal and transverse components?

Sorry if this question doesn't make sense.
Many thanks

 

[mfb]

If things don't propagate, they are not gravitational waves. You get near-field effects that are not transverse, sure. Close to the black holes, where the size of the system still matters, it is not even clear what "transverse" means exactly.

Gravitational waves are always transverse.