Large-N Gravity Toy — Full Derivation
Companion to /lab/large-n-gravity. Gravity in SPT is what is *left over* after billions of in-phase / anti-phase pulls between membrane nodes mostly cancel. The 1/N suppression naturally explains why gravity is 10⁴² times weaker than electromagnetism.
This page is the mathematical companion to /lab/large-n-gravity. The toy lets you slide N from 1 to 10⁵⁰ and watch G_eff, Hubble H₀, and the gravity-EM hierarchy ratio change. At N ≈ 1.7×10⁴², all benchmarks pass simultaneously — recovering measured Newton's G, the observed H₀, and resolving the hierarchy problem.
SPT mechanism
Formulas
Effective coupling:
G_eff(N) = G_Planck / N
Newton recovery (calibration):
G_eff = G_measured ⇔ N = N_target ≈ 1.7 × 10⁴²
Hierarchy ratio (gravity:EM at proton scale):
G m_p² / (e² / 4πε₀) ≈ 10⁻⁴²
→ identical to 1/N at N = N_target
Hubble (Friedmann):
H² = (8π G_eff / 3) ρ + Λc²/3
H₀ = H₀,ref × √(G_eff / G_measured)
At N = N_target → H₀ = 67.4 km/s/Mpc (Planck CMB)
Critical density:
ρ_c = 3 H₀² / (8π G_eff)
At N = N_target → ρ_c = 8.5 × 10⁻²⁷ kg/m³The magic number N ≈ 1.7×10⁴²
The hierarchy ratio between gravitational and electromagnetic forces between two protons is ≈ 10⁻⁴². In SPT, this is not a separate fundamental constant — it is the count of nodes whose phases cancel out gravity. The toy preset 'Recover Newton's G' snaps the slider to N = 10^42.23, at which point all four benchmarks pass simultaneously.
Benchmarks at N = 10^42.23
Mathematical soundness (preserved at all N)
- 1/r² law preserved — comes from 3D geometry of disturbance spreading, independent of N. The N-dependence is in the coupling constant, not the spatial distribution.
- Equivalence principle — universal coupling G_eff applies identically to all matter (no fifth force in this toy).
- Energy conservation — gravitational potential energy U = −G_eff m₁m₂/r is well-defined; gradient gives Newton's force.
- No tachyon — V_grav has positive curvature in attraction direction; small perturbations are stable.
Comments — Large-N Gravity Toy — Full Derivation