Understanding in 5 Minutes
A quick plain-language tour. For the derivations and equations, see the Framework page.
1. The Problem (1 min)
Two independent measurements of the universe disagree with the standard ΛCDM model in the same direction:
- S₈ tension: weak-lensing surveys measure less clustering (σ₈ ≈ 0.76–0.79) than the CMB predicts (σ₈ ≈ 0.811).
- Lyman-α suppression: the small-scale matter power spectrum is softer than expected.
2. The Mechanism (2 min)
The model treats our 3D universe as a brane in a 5D bulk. A scalar field called the radion controls the size of the extra dimension.
The radion couples to electromagnetic fields — a coupling derived from the 5D gauge action. Near z ≈ 50,000, a brief leakage event temporarily suppresses effective gravity to G_eff ≈ 0.75 G_N and imprints a cutoff on the small-scale matter power spectrum at k_c ≈ 0.75 h/Mpc.
Once the leakage settles, standard ΛCDM physics resumes. The imprint is a one-time event, not an ongoing modification.
Read the seven-brick derivation3. The Evidence (1 min)
| Observable | ΛCDM | Model | Data |
|---|---|---|---|
| σ₈ | 0.811 | ≈ 0.76 | 0.76–0.79 |
| Lyman-α k-cutoff | none | k_c ≈ 0.75 h/Mpc | suppression seen |
| G_eff at leakage | G_N | ≈ 0.75 G_N | consistent |
4. What's Next? (1 min)
- Stage 1 (Aug 2026): Boltzmann code validation (CAMB/CLASS patch).
- Stage 2 (2027): Alternative-model comparison (WDM, FDM).
- Stage 3 (2027–28): First-principles 5D derivation of Brick 4.
- Stage 4 (2028–29): Observational tests — DESI, Euclid, CMB-S4.