No black holes from cosmic string cusps
  Recent work by Jenkins and Sakellariadou claims that cusps on cosmic strings
lead to black hole production. To derive this conclusion they use the hoop
conjecture in the rest frame of the string loop, rather than in the rest frame
of the proposed black hole. Most of the energy they include is the bulk motion
of the string near the cusp. We redo the analysis taking this into account and
find that cusps on cosmic strings with realistic energy scale do not produce
black holes, unless the cusp parameters are extremely fine-tuned.
