Gravitational smoothing of kinks on cosmic string loops
  We analyze the effect of gravitational back reaction on cosmic string loops with kinks, which is an important determinant of the shape, and thus the potential observability, of string loops which may exist in the universe today. Kinks are not rounded off, but may be straightened out. This means that back reaction will only cause loops with kinks to develop cusps after some potentially large fraction of their lifetimes. In some loops, symmetries prevent even this process, so that the loop evaporates in a self-similar fashion and the kinks are unchanged. As an example, we discuss back-reaction on the rectangular Garfinkle-Vachaspati loop. 
Jeremy M. Wachter and Ken D. Olum
gr-qc astro-ph.CO