The Core Idea

One function. Three parameters. Every scale from Planck to cosmic.

C(ρ) = tanh(γ · ln(ρ/ρcrit + 1))
ρ
Presence: compatible structural elements within a system's relevancy boundary
C
Coherence: 0 = quantum, 1 = classical
γ
2/√Ncorr: coupling strength
ρcrit
A × Vflat²: transition density

Why These Specific Choices?

Why tanh?

tanh is an S-shaped curve that smoothly transitions from 0 to 1 — think of it as a dimmer switch between “fully quantum” and “fully classical.” The function must be bounded [0, 1], monotonic, and smooth. tanh arises naturally in mean-field models (e.g., the Ising model order parameter m = tanh(βJzm)). Other sigmoids (logistic, error function) share the same qualitative properties; tanh is a natural choice from the Landau theory family, not the only possible one.

Need an analogy first? · Full derivation →

Why γ = 2/√Ncorr?

The 1/√Ncorr dependence resembles central-limit-theorem scaling (fluctuations ~ 1/√N), which is generic statistics for correlated ensembles. Ncorr (number of correlated particle units) is the physically measurable quantity. The factor of 2 is motivated by phase-space arguments (6D contracted to 3 effective) but should be understood as a motivated ansatz rather than a rigorous derivation.

Full derivation →

Why log?

Density spans 80+ orders of magnitude (from interstellar gas at 10−24 g/cm³ to neutron stars at 1014 g/cm³). The logarithm compresses this range into something the tanh can work with.

What It Predicts

γ « 1: Quantum Regime

Few correlated particles, strong coherence effects. Superposition, interference, entanglement. The domain of quantum mechanics.

Validated

γ ≈ 1: The Boundary

Phase transitions, chemistry, catalysis, biology. Where quantum meets classical. 1,703 phenomena cluster here at 89% validation rate.

89% Validated

γ » 1: Classical Regime

Many correlated particles, classical behavior. Galaxy dynamics, everyday physics. The domain of Newton and general relativity.

Validated

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Related Concepts

FundamentalsThe four foundations — everything else flows from theseThe Coherence FunctionC(ρ) = tanh(γ log(ρ/ρ_crit + 1))The γ Parameterγ = 2/√N_corr: why 2, why √NScale InvarianceFrom Planck to cosmic: 80 orders of magnitude