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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

Gravity is the residual coupling. Between any two macroscopic objects, billions of node pairs contribute pulls. In-phase pairs attract; anti-phase pairs repel. The two roughly cancel — but a tiny fractional residual remains, scaling as 1/N where N is the count of phase-mixed nodes. This residual is what we measure as gravity. The hierarchy 10⁻⁴² between gravity and electromagnetism is just the value of N.

Formulas

latex
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/m³

The 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

Newton's G
Toy: G_eff = 6.674×10⁻¹¹ m³/(kg·s²). CODATA 2018: 6.67430(15)×10⁻¹¹. PASS exactly.
Hierarchy gravity:EM
Toy: ratio = 1.0 (G_eff equal to measured G). Standard Model treats this as a separate input; SPT derives it from N. PASS by construction at N = N_target.
Hubble H₀ (Planck CMB)
Toy: H₀ = 67.4 km/s/Mpc. Planck 2018: 67.4 ± 0.5. PASS. Note: SH0ES distance ladder reports 73.0 ± 1.0 — the famous 'Hubble tension' is unresolved by all theories including SPT.
Critical density ρ_c
Toy: ρ_c = 8.53×10⁻²⁷ kg/m³. Cosmology textbook: 8.5×10⁻²⁷. PASS within 0.5%.

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.

Conclusion

The hierarchy problem is not a fine-tuning miracle. In SPT, gravity is weak by factor 10⁴² because that is the count of phase-mixed nodes whose pulls cancel. Rather than asking 'why is G so small?' SPT asks 'how many nodes share the membrane between two macroscopic objects?' — and the answer is exactly 10⁴², which gives exactly the measured G. No tuning required.

CommentsLarge-N Gravity Toy — Full Derivation