Infrared modification of gravity from conformal symmetry
  We reconsider a gauge theory of gravity in which the gauge group is the
conformal group SO(4,2) and the action is of the Yang-Mills form, quadratic in
the curvature. The resulting gravitational theory exhibits local conformal
symmetry and reduces to Weyl-squared gravity under certain conditions. When the
theory is linearized about flat spacetime, we find that matter which couples to
the generators of special conformal transformations reproduces Newton's inverse
square law. Conversely, matter which couples to generators of translations
induces a constant and possibly repulsive force far from the source, which may
be relevant for explaining the late time acceleration of the universe. The
coupling constant of theory is dimensionless, which means that it is
potentially renormalizable.
