  If Lorentz symmetry is broken, it must have occurred dynamically, via a
vector or tensor field whose potential energy forces it to take on a non-zero
background expectation value "in vacuum". If the set of minima of this
potential (the vacuum manifold) has a non-trivial topology, then there can
arise topological defects: stable solutions in which the field approaches
different potential minima as we go to infinity in different directions. I
discuss the current status of research into these topological defects in the
context of Lorentz symmetry breaking, including recent results concerning the
birefringent light-bending of monopole solutions, and the search for models
supporting cosmic-string and domain-wall defects.
