I Dark matter and structure formation

[Ranku]

Could matter have formed structures in the universe, like galaxies, without the presence of dark matter?

 

[Orodruin]

Yes.

But to the extent that we are observing in our actual universe. No. The dark matter potential wells are important for structure formation.

 

[Ranku]

Yes.

But to the extent that we are observing in our actual universe. No. The dark matter potential wells are important for structure formation.

I was reading an article which says the opposite, that structures could not have formed at all without dark matter.

 

[Orodruin]

I don't see how that is the opposite of what I said.

 

[ohwilleke]

There is an argument that non-linear effects in general relativity that haven't been adequately considered could give rise to the observed amount of structure without dark matter. See Alexandre Deur, "Effect of gravitational field self-interaction on large structure formation" arxiv.org: 2108.04649 (July 9, 2021) (Accepted for publication in Phys. Lett. B) DOI: 10.1016/j.physletb.2021.136510

Modified gravity theories could also have that effect. See, e.g., Sanders 1998, McGaugh 1998, McGaugh 1999, McGaugh 2000, Sanders 2001, Nusser 2002, Stachniewicz & Kutschera 2002, McGaugh 2004, Skordis et al. 2005, Llinares et al. 2008, Feix 2016, Khoury 2016.