Brane World Cosmic String Interaction
  It is shown that brane world gravity produces an attractive force between cosmic strings, in contrast to conventional Einstein gravity. This force is sufficient for stable bound states of Type II strings (which normally repel each other) to form. There is a small separation between the strings, giving them a rope-like structure. At astronomical scales these `cosmic ropes' resemble higher winding number strings, and so all brane world cosmic strings are effectively Type I. 
Stephen C. Davis