Lambda-CDM Model

Lambda-CDM Model

The ΛCDM or Lambda-CDM model is a parametrization of the Big Bang cosmological model in which the universe contains a cosmological constant, denoted by Lambda, and cold dark matter. It is frequently referred to as the standard model of Big Bang cosmology, since it is the simplest model that provides a reasonably good match to the following observations:

• the existence and structure of the cosmic microwave background
• the large scale structure in the distribution of galaxies
• the abundances of hydrogen, helium, deuterium and lithium
• the accelerating expansion of the universe observed in the light from distant galaxies and supernovae

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 of time 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 is extended by adding cosmological inflation, quintessence, and other elements that are current areas of research in cosmology. Some alternative models challenge the assumptions of the ΛCDM model, such as modified Newtonian dynamics, modified gravity, and large-scale variations in the matter density of the universe.