Friedmann–Lemaître–Robertson–Walker metric

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The Friedmann–Lemaître–Robertson–Walker metric (FLRW; ) is a metric that describes a homogeneous, isotropic, expanding (or otherwise, contracting, oscillating or constant) universe that is path-connected, but not necessarily simply connected. The general form of the metric follows from the geometric properties of homogeneity and isotropy. Depending on geographical or historical preferences, the set of the four scientists – Alexander Friedmann, Georges Lemaître, Howard P. Robertson, and Arthur Geoffrey Walker – is variously grouped as Friedmann, Friedmann–Robertson–Walker (FRW), Robertson–Walker (RW), or Friedmann–Lemaître (FL). When combined with Einstein's field equations, the metric gives the Friedmann equations, which have been developed into the Standard Model of modern cosmology and further developed into the Lambda-CDM model.

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