Lambda-CDM model: Difference between revisions

Revision as of 21:56, 18 July 2025

Revision as of 21:14, 23 July 2025

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==== Fast galaxy bar problem ====

If galaxies were embedded within massive halos of [[cold dark matter]], then the bars that often develop in their central regions would be slowed down by [[dynamical friction]] with the halo. This is in serious tension with the fact that observed galaxy bars are typically fast.<ref name="Roshan2021">{{Cite journal|last1=Mahmood|first1=R|last2=Ghafourian|first2=N|last3=Kashfi|first3=T|last4=Banik|first4=I|last5=Haslbauer|first5=M|last6=Cuomo|first6=V|last7=Famaey|first7=B|last8=Kroupa|first8=P|date=2021-11-01|title=Fast galaxy bars continue to challenge standard cosmology|journal=Monthly Notices of the Royal Astronomical Society|volume=508|issue=1|pages=926–939|doi=10.1093/mnras/stab2553|doi-access=free|arxiv=2106.10304|bibcode=2021MNRAS.508..926R|hdl=10023/24680|issn=0035-8711}}</ref>

==== Small scale crisis ====

Comparison of the model with observations may have some problems on sub-galaxy scales, possibly predicting [[Dwarf galaxy problem|too many dwarf galaxies]] and too much dark matter in the innermost regions of galaxies. This problem is called the "small scale crisis".<ref>{{Cite journal

| title =Synopsis: Tackling the Small-Scale Crisis

|journal = Physical Review D|volume = 95|issue = 12|page = 121302| last =Rini

| first =Matteo

|doi = 10.1103/PhysRevD.95.121302|year = 2017|arxiv = 1703.10559|bibcode = 2017PhRvD..95l1302N|s2cid = 54675159}}</ref> These small scales are harder to resolve in computer simulations, so it is not yet clear whether the problem is the simulations, non-standard properties of dark matter, or a more radical error in the model.

==== High redshift galaxies ====