Эйнштейннің өріс теңдеулеріне космологиялық шешім: де Ситтер әлемі

Cosmological solution to the Einstein field equations of general relativity

A de Sitter universe is a cosmological solution to the Einstein field equations of general relativity, named after Willem de Sitter. It models the universe as spatially flat and neglects ordinary matter, so the dynamics of the universe are dominated by the cosmological constant, thought to correspond to dark energy in our universe or the inflaton field in the early universe. According to the models of inflation and current observations of the accelerating universe, the concordance models of physical cosmology are converging on a consistent model where our universe was best described as a de Sitter universe at about a time seconds after the fiducial Big Bang singularity, and far into the future.

The exponential expansion of the scale factor means that the physical distance between any two non accelerating observers will eventually be growing faster than the speed of light. At this point those two observers will no longer be able to make contact. Therefore, any observer in a de Sitter universe would have cosmological horizons beyond which that observer can never see nor learn any information. If our universe is approaching a de Sitter universe then eventually we will not be able to observe any galaxies other than our own Milky Way (and any others in the gravitationally bound Local Group, assuming they were to somehow survive to that time without merging).

The Benchmark Model is a model consisting of a universe made of three components – radiation, ordinary matter, and dark energy – that fit current data about the history of the universe. These components make different contributions to the expansion of the universe as time elapses. Specifically, when the universe is radiation dominated, the expansion factor scales as , and when the universe is matter dominated Since both of these grow slower than the exponential, in the future the scale factor will be dominated by the exponential factor representing the pure de Sitter universe. The point at which this starts to occur is known as the matter lambda equivalence point and the modern day universe is believed to be relatively close to this point.