SCIENCE - Can dark energy be explained by symmetrons?

(Phys.org)-A field that permeates the universe and gives rise to a new force, or "fifth force," between massive objects may be a candidate for dark energy and an explanation for why the expansion of the universe is accelerating. This field, called the symmetron field, is so named because it has a symmetry in regions of high density, while in regions of low density, such as a vacuum, the symmetry is broken and the field mediates the new force.

http://phys.org/news/2013-01-dark-energy-symmetrons.htm