Dark Matter could explain the presence of gravitational waves prior to the Big Bang.
Einstein's geometric gravity
The key idea of Einstein's theory of general relativity is that gravity is not an ordinary force, but rather a property of space-time geometry. The following simplified analogy, which substitutes a two-dimensional surface for four-dimensional space-time, serves to illustrate this idea.
Imagine empty space - in our case, a two-dimensional plane - with no forces acting between the bodies floating around. If there are no forces, then classical mechanics and Einstein's mechanics of special relativity are in agreement: Under these circumstances, bodies move along the straightest possible lines (which in this case are just straight lines in space) with a constant velocity. In the following image, this is symbolized by the straight paths of two particles A and B:
It could be that Dark Matter is representing two different bodies from a single body with a constant velocity being present that would create a gravitational wave.
Think of Dark Matter on the inside of a tube. Although Dark Matter is considered a single mass two points on the interior of the tube within the Dark Matter mass moving at a constant velocity traveling in the same direction regardless of whether that direction in a forward or reverse direction would never meet at all. But if those same two points along with Dark Matter are place on the inside of a tube and the tube rotated in a clockwise or counter-clockwise manner then the two points rotating at a constant velocity would encounter each other 60 seconds of every minute, every minute of every hour, of every hour of every day and every day of every week to create a potential for Dark Matter gravitational waves.
So maybe the graviton wave does exist in the realm of Dark Matter. it would seem to me that that reason why we can't measure it is because it traveling faster than the speed of light.
If the speed of light is set at the Universal top speed then another velocity slightly faster than the speed of light would be present.
If two cars one weighing 1 ton and another weighing 5 tons are placed front to front and both accelerate to 50 miles per hour which vehicle actually moves the farthest? Both vehicles move the farthest because one is being pushed by the other.
Rather which one will be pushed? Regardless of the velocity of either vehicle the vehicle with more mass would push the smaller vehicle with less mass.
What this could mean is that gravitational waves although having the same velocity could have different mass characteristics where Dark Matter gravitational waves would have slightly less mass than the objects within the mass of Dark Matter are generating thus allowing the expansion of space-time.
http://www.einstein-online.info/elementary/generalRT/GeomGravity
