Theories of Dark Energy with Screening Mechanisms
  Despite the overwhelming evidence for the existence of dark energy and dark
matter, their underlying fundamental physics remains unknown. This review
article explores the tantalizing possibility that the dark sector includes new
light degrees of freedom that mediate long-range forces on cosmological scales.
To ensure consistency with laboratory and solar system tests of gravity, some
screening mechanism is necessary to "hide" these degrees of freedom locally. I
will focus on two broad classes of screening theories, chameleons and
symmetrons, which rely respectively on the scalar field acquiring a large mass
or weak coupling in the presence of large ambient matter density.
