  The idea that dark energy is gravitational waves may explain its strength and
its time-evolution provided that the additional energy comes from a background.
A possible concept is that dark energy is the ensemble of coherent bursts
(solitons) of gravitational waves originally produced by stimulated emission
when the first generation of super-massive black holes was formed. These
solitons get their initial energy as well as keep up their energy density
throughout the evolution of the universe by stimulating emission from a
background brane. We model this process by working out this energy transfer in
a Boltzmann equation approach. The transit of these gravitational wave solitons
may be detectable. Key tests include pulsar timing, clock jitter and the radio
and neutrino backgrounds.
