GR says that monopole gravitational radiation does not exist. I understand the reasons for this.
However there is this effect (which seems to me to have the hallmarks of a wave). Paper at arXiv:
Monopole gravitational waves from relativistic fireballs driving gamma-ray bursts (http://arxiv.org/abs/astro-ph/0309448)
I would like some feedback on that paper, my thoughts on it are below, which may or may not be relevant.
Basically what happens is that you have a mass that sheds energy. So if you are standing at a point outside the mass, the gravitational potential changes very quickly as the ejected mass passes by you. Since we detect the gravitational field as the slope of the potential, it seems there will be a boost applied to our motion as the potential changes.
This change in motion is why I think that the paper has the correct name - these are waves.
The author of the paper had no trouble calling this effect a monopole gravitational wave, but is it properly called a gravitational wave?