Analysis: 120 Orders of Magnitude Increase in Cosmological Constant
1. Understanding the Question
The cosmological constant Λ in Einstein's equations relates to dark energy density ρΛ by:
ρΛ = Λc²/8πG
In natural units (c = ℏ = 1), Λ has units of [length]−2. The measured value is approximately:
Λobs ≈ 1.1 × 10−52 m−2
The Planck length is ℓP ≈ 1.6 × 10−35 m, and the Planck epoch is tP ≈ 5.4 × 10−44 s.
The question considers Λ increased by 10120 times its observed value, and asks whether the resulting expansion rate corresponds to timescales shorter than the Planck time.
2. Relating Λ to Expansion Rate
In a de Sitter universe dominated by Λ, the Hubble parameter is:
H = c√(Λ/3)
For the observed Λ:
Hobs ≈ 1.82 × 10−18 s−1
Hubble time Tobs = 1/Hobs ≈ 5.5 × 1017 s (∼17 billion years)
3. Scaling Λ by 10120
New cosmological constant:
Λnew = 10120 × Λobs ≈ 1.1 × 1068 m−2
New Hubble parameter:
Hnew ≈ 1.82 × 1042 s−1
4. Resulting Timescale
New Hubble time:
Tnew = 1/Hnew ≈ 5.5 × 10−43 s
Planck time tP ≈ 5.4 × 10−44 s
Tnew is about 10 times longer than tP
5. Planck Units Interpretation
In Planck units (ℓP = tP = 1):
Λobs/ℓP−2 ≈ 2.8 × 10−122
Multiplying by 10120 gives Λ ∼ ℓP−2, so H ∼ tP−1
This means TH ∼ tP exactly
6. Conclusion
With Λ increased by 10120 in Planck units, the Hubble time equals the Planck time. The expansion rate reaches the Planck scale, entering the quantum gravity regime.
Answer: Yes
No comments:
Post a Comment