 |
| Alexander Friedmann (Александр Фридман) |
This post completes a previous post with a similar title:
The problem of the cosmological constant.First of all, we should define three different
concepts that could be closely related:
- Vacuum energy: due to the constant appearance of pairs of
particles and antiparticles that immediately mutually disintegrate, so they
are undetectable through direct experimentation. Their appearance is a
consequence of the uncertainty principle: ΔE×Δt<ħ/2,
which implies that a particle with energy ΔE
can appear spontaneously during a time Δt<ħ/(2ΔE),
which is smaller for larger ΔE.
Thus, a virtual electron would last less than 4×10-21 seconds.
A proton, whose mass is 1837 times greater, would last 1837 times less. By
applying quantum field theory to all the known particles, the energy of
the vacuum can be estimated.
- The cosmological constant: introduced by Einstein in his cosmological equation, which in the format devised by Alexander Friedman is expressed as follows: The symbol Λ is the cosmological constant. Einstein proposed a negative value, to compensate for a cosmic expansion, in which he initially did not believe. Today it is thought to be positive, which would explain the accelerated expansion of the universe discovered in 1998.
- Dark energy: an unknown agent that would cause the accelerated expansion of the universe.
