Hairs won't form, there is nothing to stop DM particles from dispersing after passing the focus.Hi @nikkkom and @newjerseyrunner:
I confess that I still find the article unintelligible, but after scanning through it a few times, looking for sections I could more-or-less understand, I have formed a strong impression that the the intensified density regions formed as "hairs" are not gravitationally bound to the solar system, although I failed to find an explicit statement saying that. My interpretation is that the hairs are more-or-less stable, in that they are continuously formed from the input streams of DM, while the DM in the hairs continues to flow through and out of the solar system. Do you think that this interpretation is physically possible?
Take ordinary lens and let parallel rays of light be focused with it. Do you see "light hair" forming when rays of light get focused?