system
Given the following post, respond as if you're commenting on Reddit:
human
Regarding dark matter, if what we believe about it is true, shouldn't there be dark matter black holes all over the universe?

This thought was sparked my another question in this sub. If it is true that dark matter is so common, and it only interacts via gravity, there would be no other forces involved that would result in star formation, so shouldn't it just collect into dense areas and form black holes bypassing all of the star formation and supernovae that are nomally required for black hole formation?
gpt
For things to condense to the densities required to form black holes, you need a way for the particles to lose energy and slow down, stick together and clump. With normal matter, electromagnetism gets the job done by allowing collisions and radiating energy into space, this method is unavailable to dark matter.

If you have two particles of dark matter separated by some distance, they'll simply attract, fall into each other and then pass right by without losing energy^1 , they'll fly apart and eventually be pulled back toward each other and just oscillate (or orbit) forever. With a lot of dark matter, this results in a diffuse cloud, it's not even a disk shape because collisions allow the disk shape to form.

^1 There is radiative loss in the form of gravitational waves, but this would be so small as to not matter.