Lifshitz Singularities
  Lifshitz spacetimes are possible gravitational duals to strongly coupled field theories with an anisotropic scaling symmetry. These spacetimes however, have a null curvature singularity. We find that higher dimensional embeddings of Lifshitz also have a similar singularity. We study the propagation of test strings in this background and find that they become infinitely excited if they try to propagate through the singularity. This means that the Lifshitz geometry is unstable and will receive large corrections in string theory. 
Gary T. Horowitz and Benson Way
hep-th