> these findings provide an unambiguous signature of a dark matter behavior that exhibits collisional properties in a very energetic high-redshift cluster colli

> these findings provide an unambiguous signature of a dark matter behavior that exhibits collisional properties in a very energetic high-redshift cluster collision. ooh, what if dark matter _used_ to be much more self-interacting, and now isn't? iirc, "high-redshift" means it's very far away from us, and thus what we're seeing is pretty old...