|
==== Violations of homogeneity ====
The homogeneity of the universe needed for the ΛCDM applies to very large volumes of space.
Based on [[N-body simulation]]s in ΛCDM, Yadav and his colleagues showedshow that the spatial distribution of galaxies is statistically homogeneous if averaged over scales 260[[Parsec#Megaparsecs and gigaparsecs|/h Mpc]] or more.<ref name=Yadav>{{cite journal|last=Yadav|first=Jaswant |author2=J. S. Bagla |author3=Nishikanta Khandai|title=Fractal dimension as a measure of the scale of homogeneity|journal=Monthly Notices of the Royal Astronomical Society|date=25 February 2010|volume=405|issue=3|pages=2009–2015|doi=10.1111/j.1365-2966.2010.16612.x |doi-access=free |arxiv = 1001.0617 |bibcode = 2010MNRAS.405.2009Y |s2cid=118603499 }}</ref> However, many large-scale structures have been discovered, and some authors have reported some of the structures to be in conflict with the predicted scale of homogeneity for ΛCDM, including
* The [[Clowes–Campusano LQG]], discovered in 1991, which has a length of 580 Mpc
OtherNumerous authorsclaims claimof thatlarge-scale thestructures existencereported ofto structuresbe largerin thanconflict with the predicted scale of homogeneity in thefor ΛCDM model doesdo not necessarilywithstand violate the cosmological principle in the ΛCDMstatistical modelanalysis.<ref name=Nadathur>{{cite journal|last=Nadathur|first=Seshadri|title=Seeing patterns in noise: gigaparsec-scale 'structures' that do not violate homogeneity|journal=Monthly Notices of the Royal Astronomical Society|date=2013|volume=434|issue=1|pages=398–406|doi=10.1093/mnras/stt1028|doi-access=free |arxiv=1306.1700|bibcode =2013MNRAS.434..398N|s2cid=119220579}}</ref><ref name="Snowmass21"/> {{rp|7.8}}▼* The [[Sloan Great Wall]], discovered in 2003, which has a length of 423 Mpc<ref name=apj624_2_463>{{Cite journal | display-authors=1 | last1=Gott | first1=J. Richard III | last2=Jurić | first2=Mario | last3=Schlegel| first3=David | last4=Hoyle | first4=Fiona | last5=Vogeley | first5=Michael | last6=Tegmark | first6=Max | last7=Bahcall | first7=Neta |last8=Brinkmann | first8=Jon | title=A Map of the Universe | journal=The Astrophysical Journal | volume=624 | issue=2 | pages=463–484 |date=May 2005 | doi=10.1086/428890 | bibcode=2005ApJ...624..463G |arxiv = astro-ph/0310571| s2cid=9654355 }}</ref>
* [[U1.11]], a [[large quasar group]] discovered in 2011, which has a length of 780 Mpc
* The [[Huge-LQG]], discovered in 2012, which is three times longer than and twice as wide as is predicted possible according to ΛCDM
* The [[Hercules–Corona Borealis Great Wall]], discovered in November 2013, which has a length of 2000–3000 Mpc (more than seven times that of the [[Sloan Great Wall|SGW]])<ref>{{cite arXiv |eprint=1311.1104|last1= Horvath|first1= I.|title= The largest structure of the Universe, defined by Gamma-Ray Bursts|last2= Hakkila|first2= J.|last3= Bagoly|first3= Z.|class= astro-ph.CO|year= 2013}}</ref>
* The [[The Giant Arc|Giant Arc]], discovered in June 2021, which has a length of 1000 Mpc<ref>{{Cite web|url=https://www.newscientist.com/article/2280076-line-of-galaxies-is-so-big-it-breaks-our-understanding-of-the-universe/|title = Line of galaxies is so big it breaks our understanding of the universe}}</ref>
* The [[Big Ring]], reported in 2024, which has a diameter of 399 Mpc and is shaped like a ring<ref>{{cite news |last1=Cooper |first1=Keith |date=22 January 2024 |title=An impossibly huge ring of galaxies might lead us to new physics. Here's how |url=https://www.space.com/big-ring-galactic-superstructure-celestial-anomaly |access-date=31 January 2024 |work=Space.com |language=en}}</ref>
▲Other authors claim that the existence of structures larger than the scale of homogeneity in the ΛCDM model does not necessarily violate the cosmological principle in the ΛCDM model.<ref name=Nadathur>{{cite journal|last=Nadathur|first=Seshadri|title=Seeing patterns in noise: gigaparsec-scale 'structures' that do not violate homogeneity|journal=Monthly Notices of the Royal Astronomical Society|date=2013|volume=434|issue=1|pages=398–406|doi=10.1093/mnras/stt1028|doi-access=free |arxiv=1306.1700|bibcode =2013MNRAS.434..398N|s2cid=119220579}}</ref><ref name="Snowmass21"/>
=== El Gordo galaxy cluster collision ===
| 