Lemaître–Tolman metric
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In physics, the Lemaître–Tolman metric, also known as the Lemaître–Tolman–Bondi metric or the Tolman metric, is a Lorentzian metric based on an exact solution of Einstein's field equations; it describes an isotropic and expanding (or contracting) universe which is not homogeneous,[1][2] and is thus used in cosmology as an alternative to the standard Friedmann–Lemaître–Robertson–Walker metric to model the expansion of the universe.[3][4][5] It has also been used to model a universe which has a fractal distribution of matter to explain the accelerating expansion of the universe.[6] It was first found by Georges Lemaître in 1933[7] and Richard Tolman in 1934[1] and later investigated by Hermann Bondi in 1947.[8]