کاروژ ِ خلاء kâruž-e xala'
*Fr.: énergie du vide*
In particle physics the lowest energy allowed by field quantization when all fields are
in their → *ground state*s. Vacuum energy is predicted to arise from
→ *virtual particle*s that fluctuate in and out of existence,
as manifested by the → *Casimir effect*.
The cosmological → *dark energy* is postulated to be related
to vacuum fluctuations. There is however an enormous discrepancy with the predictions of
quantum field theory. In this theory the value of vacuum energy density is expected
to be roughly of the order
ρ_{v}≅ *E*_{max}^{4},
where *E*_{max} is the maximum energy at which the field theory is valid.
At energies of the order of the
→ *Planck energy*,
*E*_{Pl}≅ 10^{19} GeV, vacuum energy might be roughly:
ρ_{v}≅ *E*_{Pl}^{4}≅ 10^{76} GeV^{4}.
On the other hand, the vacuum energy density in standard cosmological model
is given by:
ρ_{Λ} = Ω_{Λ}.ρ_{crit}, where
Ω_{Λ} is the → *density parameter* for the
→ *cosmological constant* and ρ_{crit}
is the → *critical density*. More explicitly,
*ρ*_{Λ} = Ω_{Λ} . 3 H^{2}/(8πG).
Using
present-day values of Ω_{Λ} (0.7) and *H* (70) leads to
ρ_{Λ} = 10^{-46} GeV^{4}. Therefore,
the discrepancy between the prediction and the observed value is 122 orders
of magnitude. → *vacuum*; → *energy*. |