Accelerating black hole in 2+1 dimensions and 3+1 black (st)ring
  A C-metric type solution for general relativity with cosmological constant is
presented in 2+1 dimensions. It is interpreted as a three-dimensional black
hole accelerated by a strut. Positive values of the cosmological constant are
admissible too. Some embeddings of this metric in the 3+1 space-time are
considered: accelerating BTZ black string and a black ring where the
gravitational force is sustained by the acceleration.
