Could dark energy be coming from the constant creation and annihilation of matter-anti matter pairs that form spontaneously in the vacuum of deep space?
No, you actually don't get any energy out of this process. The amount of energy that is released when matter and anti-matter annihilate is exactly the same amount of energy that is required to create the matter anti-matter pair in the first place! To "gain" energy, you would need to only have the annihilation step, which means you would need a pre-existing matter anti-matter pair, but that isn't a particularly common situation in the universe. Also, the energy that is produced during annihilation comes out in a very recognizable form: light! (specifically, high energy light, i.e. x-rays or gamma rays depending on the mass of the matter being annihilated) So it can't be the source of dark energy, because we would be able to detect it if a lot of it were out there.
This page was last updated June 27, 2015.