Macroscopic gravitational wave is already established, now that we have a direct observation of it. Can we observe a microscopic version of it? How about a soliton type gravitational wave?
In Belinki's book above there is a complete classification of GR's solitons. In some Belinski et al papers there are some speculations about the formation of GR solitonic waves during early universe and their decays into standard gravitational waves