De Sitter universe

By using the de Sitter universe instead, where the expansion is truly exponential, there are many simplifications.

Eventually there will be almost nothing left but the cosmological constant, and our universe will have become a de Sitter universe.

A de Sitter universe has no ordinary matter content but with a positive cosmological constant () which sets the expansion rate, .

In particular O(4,1) is the isometry group of the de Sitter universe dS, a cosmological model.

Therefore any observer in a de Sitter universe would see event horizons beyond which that observer can never see nor learn any information.

An example of a cosmological model with an event horizon is a universe dominated by the cosmological constant (a de Sitter universe).

A de Sitter universe is a cosmological solution to Einstein's field equations of General Relativity which is named after Willem de Sitter.

For the case of a horizon perceived by an occupant of a de Sitter Universe, the horizon always appears to be a fixed distance away for a non-accelerating observer.

He also came up with the concept of the de Sitter space and de Sitter universe, a solution for Einstein's general relativity in which there is no matter and a positive cosmological constant.

This exponential dependence on time makes the spacetime geometry identical to the de Sitter Universe, and only holds for a positive sign of the cosmological constant, the sign that was observed to be realized in Nature anyway.

In 1988, Hideo Kodama wrote down the equations of the Kodama state, but as it described a positive (de Sitter universe) spacetime, which was believed to be inconsistent with observation, it was largely ignored.

After Leonard Susskind proposed the black hole complementarity conjecture for black holes in quantum gravity, he realized it would also apply to a de Sitter universe with a positive cosmological constant with the cosmological horizon in place of the event horizon.

Note this is not the same thing as solving Einstein's field equations for general relativity to get a de Sitter Universe, rather de Sitter relativity is about getting a de Sitter Group for special relativity which neglects gravity.

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).

Since the simplest cosmological model (the De Sitter universe) that solves that equation is a spherically symmetric, stationary, closed universe (exhibiting a cosmological red shift, which is more conventionally interpreted as due to expansion), it seemed to explain the overall form of the universe.

An even simpler generalization, the Schwarzschild-de Sitter lambdavacuum solution (sometimes called the Köttler solution), which models a spherically symmetric massive object immersed in a de Sitter universe, is an example of an asymptotically simple spacetime which is not asymptotically flat.

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.

In 1924 he obtained more precise results, and interpreted them both as a confirmation of an increase of radial velocities with distance, but also as confirmation of a de Sitter universe, in which the increase of redshift is seen as caused by an increased time dilation in distant parts of the universe.