But no gravitational acceleration is 100% efficient. Eventually some of these wimps would be slowed down somewhere in the universe. If the gravitational field were large enough, they'd be brought to a complete stop. Right?
So what these astro types are trying to tell me is that this hasn't happened anywhere? That makes no sense. Also if the stuff is moving at light speed pretty much randomly, how does it form 'clouds' (for lack of a better word) that causes this lensing effect?
Logic would dictate that they're flying in all directions instead of forming vast clouds that can 'lens' light.
Right?
L
THey'll stop only at the event horizon of a black hole. They can be slowed, only after leaving the region os a galaxy, but in that case they'll be accelerated back again to their original speed when they return to the galaxy.
Let's say they're slowed for that reason. Then they're captured by a relatively slow moving large object. They will collect in and around the center of the object, because they are weakly interacting. They will never sit on the surface, because the surface layers offer no impediment to their motion. Most likely, they will simply be rendered into eccentric orbits that pass through the object.
Regardless, the gravitational field of the nearby galaxy that holds that particle, will also grab the big object and haul it in. Since the WIMP has it's orbit in the galactic field, the other object has it's own orbit in that field and all the WIMP is held by is gravity, the WIMP will be torn away again by the galctic field and return to it's oriignal v in it's orbit. Effectively, no relatively amall and lone object, other than black holes, can grab one. They can only provide the impediment of a particle cloud and temporary gravitational bump.
"Logic would dictate that they're flying in all directions instead of forming vast clouds that can 'lens' light."
Neutrinos are flying in all directions as they are being created. Axions were created around the time quarks condensed after the big bang. They follow the expansion of the universe and such things as black hole and galaxy formation.
"Also if the stuff is moving at light speed pretty much randomly, how does it form 'clouds' (for lack of a better word) that causes this lensing effect?"
the clouds of them in spiral galaxies are understood as orbits around and through the galaxy. THe same would happen around a black hole. Those regions containing many orbits would lens.
Cluster galaxies have little, or no spin. The particles could just be in orbits with no net angular momentum. That would be trivial, but no one's done the calcs and reported them yet. I don't know much about clusters, such as formation, ect... , so I can't say much.