CSL-1: Lensing by a Cosmic String or a Dark Matter Filament?
  The lens candidate CSL-1 has been interpreted as evidence for a cosmic string. Here we test the hypothesis that the lensing comes from a tidally disrupted dark matter halo. We calculate the mass-density relationship that one would expect from structure formation theory and come to the conclusion that in order to explain the lensing using dark matter, the halo would have to have a mass greater than the Milky Way. There is apparently no such object seen in the data. If the follow up observations confirm that the two objects are indeed images of the same galaxy, then it seems difficult to explain the lens using dark matter. 
Malcolm Fairbairn (Stockholm University)