de Sitter Universe
giti-ye de Sitter
Fr.: Univers de de Sitter
A solution to → Einstein's field equations of → general relativity which contains no ordinary matter (ΩM = 0) or radiation (ΩR = 0), is → Euclidean (k = 0), but has a → cosmological constant (ΩΛ > 0). The Universe expands exponentially forever. This solution was the first model expanding of → expanding Universe. See also → empty Universe, → Milne Universe.
After the Dutch mathematician and physicist Willem de Sitter (1872-1934) who worked out the model in 1917; → universe.
Einstein-de Sitter Universe
giti-ye Einstein-de Sitter
Fr.: Univers Einstein-de Sitter
The → Friedmann-Lemaitre model of → expanding Universe that only contains matter and in which space is → Euclidean (ΩM > 0, ΩR = 0, ΩΛ = 0, k = 0). The Universe will expand at a decreasing rate for ever.