This is something new. The simulations suggest shocks of radiation from very early in BB history, 10^-30 seconds after BB to about 1/10 of a millisecond, radiation from that time could form shock waves strong enough to generate gravity waves but would be stretched out in time to what I calculated to be a wavefront taking 3800 years to complete. They claim they could detect that long a wavelength, a wavelength of 3800 light years. Only about 40 or so waves would go by in the entire milky way galaxy or be in the whole galaxy at the same time.
Don't know how they think they would manage to detect such waves, since the ones they detected was about 100 hertz.