What Gravitational Waves Can Say About Dark Matter

<i>Dark matter seems to interact with normal matter only through gravity, but, based on the way known particles interact, theorists think it’s possible that dark matter might also interact with itself.</i><p>If dark matter were to interact with itself (as regular matter does), wouldn&#x27;t we expect it to clump together and form the same structures as regular matter does, especially given that there&#x27;s supposed to be much more dark matter to interact together than the regular stuff? AIUI one of the defining features of dark matter is that it <i>doesn&#x27;t</i> clump together.

Perhaps tangential, but is there a frequency of a gravity wave high enough to &quot;cusp&quot; due to one of the quantization limits?

Tangential, and possibly revealing ignorance here. I definitely don&#x27;t get why clouds of dark matter surrounding galaxies don&#x27;t fall into the black hole at the center. Dark matter is there to explain why the outer stars of a galaxy rotate faster than expected, but why is dark matter not distributed roughly in the same density distribution as visible matter?

TFA doesn&#x27;t mention recent evidence that primordial black holes are rare. It also doesn&#x27;t address issues around condensation of dark matter. That is, two dark-matter objects can&#x27;t collide, because they&#x27;ll just pass through each other.

They say, in a whisper, &quot;Don&#x27;t get a degree in particle physics! It&#x27;s oversaturated, and the field can&#x27;t even justify building another particle accelerator because it doesn&#x27;t know what to look for!&quot;