Massive mimetic cosmology
  We study the first cosmological implications of the mimetic theory of massive
gravity recently proposed by Chamseddine and Mukhanov. This is a novel theory
of ghost-free massive gravity which additionally contains a mimetic dark matter
component. In an echo of other modified gravity theories, there are
self-accelerating solutions which contain a ghost instability. In the
ghost-free region of parameter space, the effect of the graviton mass on the
cosmic expansion history amounts to an effective negative cosmological
constant, a radiation component, and a negative curvature term. This allows us
to place constraints on the model parameters---the graviton mass and the
St\"uckelberg vacuum expectation value---by insisting that the effective
radiation and curvature terms be within observational bounds. The late-time
acceleration must be accounted for by a separate positive cosmological constant
or other dark energy sector. We impose further constraints at the level of
perturbations by demanding linear stability. We comment on the possibility of
distinguishing this theory from $\Lambda$CDM with current and future
large-scale structure surveys.
