There’s an article on Ars Technica with the sub-tilte “Neutron stars’ failure to collapse into black holes limit dark matter.”
http://arstechnica.com/science/2012/07/neutron-stars-and-black-holes-illuminate-dark-matter/
What’s the article got to do with the title I don’t know (besides a pun on words).
It’s based on the article “Limits on Self-Interacting Dark Matter from Neutron Stars” on Physical Review Letters:
http://prl.aps.org/abstract/PRL/v108/i19/e191301