Editing Lambda-CDM model (section)

{{Short description|Mathematical model of the Big Bang}}
{{Redirect|Standard cosmological model|other uses|Standard model (disambiguation)}}
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{{Cosmology|comp/struct}}

The '''Lambda-CDM''', '''Lambda cold dark matter''', or '''ΛCDM''' model is a [[mathematical model]] of the [[Big Bang]] theory with three major components:
# a [[cosmological constant]], denoted by [[lambda]] (Λ), associated with [[dark energy]];
# the postulated [[cold dark matter]], denoted by CDM;
# ordinary [[matter]].

It is the current ''standard model'' of Big Bang cosmology,<ref name=DeruelleUzan>{{Cite book |last1=Deruelle |first1=Nathalie |url=https://academic.oup.com/book/43967 |title=Relativity in Modern Physics |last2=Uzan |first2=Jean-Philippe |date=2018-08-30 |publisher=Oxford University Press |isbn=978-0-19-878639-9 |editor-last=de Forcrand-Millard |editor-first=Patricia |edition=1 |language=en |doi=10.1093/oso/9780198786399.001.0001 |author-link=Nathalie Deruelle |author-link2=Jean-Philippe Uzan}}</ref> as it is the simplest model that provides a reasonably good account of:
* the existence and structure of the [[cosmic microwave background]];
* the [[Observable universe#Large-scale structure|large-scale structure]] in the distribution of galaxies;
* the observed [[abundance of the chemical elements|abundances]] of [[Big Bang nucleosynthesis|hydrogen (including deuterium), helium, and lithium]];
* the [[accelerating expansion of the universe]] observed in the light from distant [[Galaxy|galaxies]] and [[supernova]]e.

The model assumes that [[general relativity]] is the correct theory of gravity on cosmological scales. It emerged in the late 1990s as a '''concordance cosmology''', after a period when disparate observed properties of the universe appeared mutually inconsistent, and there was no consensus on the makeup of the energy density of the universe.

The ΛCDM model has been successful in modeling a broad collection of astronomical observations over decades. Remaining issues challenge the assumptions of the ΛCDM model and have led to many alternative models.<ref name="Snowmass21"/>