Lambda-CDM model

Lambda-CDM is the cosmological model in which the universe’s large-scale evolution follows general relativity and is shaped chiefly by cold dark matter and a cosmological constant.

General relativity: Albert Einstein’s theory of gravity describes gravitation as the curvature of spacetime caused by energy and matter. It supplies the gravitational framework for the model’s cosmic expansion and structure growth.
Cosmic inflation: A proposed brief period of extremely rapid expansion in the very early universe. Inflation offers an origin for the initial fluctuations that later structure growth amplifies.
Planck satellite: A European Space Agency spacecraft that mapped the cosmic microwave background from 2009 to 2013. Its precise sky maps produced some of the model’s tightest parameter constraints.
Einstein–de Sitter universe: A spatially flat cosmological model containing only pressureless matter, with no cosmological constant or radiation. It lacks the late-time acceleration required to fit supernova observations.
Edwin Hubble: An American astronomer whose observations established that galaxies exist beyond the Milky Way and recede with distance. His evidence for cosmic expansion helped establish the observational basis of modern cosmology.
Friedmann equations: Equations derived from general relativity that describe how a homogeneous, isotropic universe expands over time. They translate the model’s contents into predictions for the universe’s expansion history.
Cosmic expansion: The increase over time in distances between widely separated, unbound regions of the universe. Expansion is the evolving quantity described by the model’s background solution.
Type Ia supernova: A thermonuclear stellar explosion whose relatively uniform peak brightness makes it useful as a distance indicator. Their distances and redshifts revealed the universe’s late-time accelerated expansion.
Quintessence: A proposed dynamical scalar field whose changing energy density could drive cosmic acceleration. Unlike a constant Lambda, it allows dark energy to vary over time.
Georges Lemaître: A Belgian physicist and Catholic priest who developed an expanding-universe model and proposed an early, dense cosmic state. His theoretical work anticipated key features of modern expanding-universe cosmology.

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