Collapse of Randomly Linked Polymers
  We consider polymers in which M randomly selected pairs of monomers are restricted to be in contact. Analytical arguments and numerical simulations show that an ideal (Gaussian) chain of N monomers remains expanded as long as M<<N. This result is inconsistent with results obtained from free energy considerations by Brygelson and Thirumalai (PRL76, 542 (1996)). 
Yacov Kantor (Tel Aviv U.) and Mehran Kardar (MIT)