Lambda-CDM model

ΛCDM or Lambda-CDM is an abbreviation for Lambda-Cold Dark Matter. It represents the current concordance model of big bang cosmology that explains cosmic microwave background observations, as well as large scale structure observations and supernovae observations of the accelerating expansion of the universe. It is the simplest model that is in agreement with all the observations.

Related Topics:
Big bang - Cosmology - Cosmic microwave background - Large scale structure - Supernova - Expansion of the universe

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• Λ (Lambda) stands for the cosmological constant which is a dark energy term that allows for the current accelerating expansion of the universe. Currently, approximately 70% of the energy density of the present universe is in this form.
• Cold dark matter is the model where the dark matter is explained as being cold (i.e. not thermalized), non-baryonic, collisionless dust. This component makes up 26% of the energy density of the present universe. The remaining 4% is all of the matter and energy that makes up the atoms and photons that are the building blocks of planets, stars, and gas clouds in the universe.
• The model assumes a nearly scale-invariant spectrum of primordial perturbations and a universe without spatial curvature. It also assumes that it has no observable topology, so that the universe is much larger than the observable particle horizon. These are predictions of cosmic inflation.

These are the simplest assumptions for a consistent, physical model of cosmology. However, ΛCDM is a model. Cosmologists anticipate that not all of them will not be borne out exactly, when more is known about the fundamental physics. In particular, cosmic inflation predicts spatial curvature at the level of 10−4 to 10−5. It would also be surprising if the temperature of dark matter were absolute zero. Moreover, ΛCDM says nothing about the fundamental physical origin of dark matter, dark energy and the nearly scale-invariant spectrum of primordial curvature perturbations: in that sense, it is merely a useful parameterization of ignorance.

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Lambda-CDM model: Parameters ►