Parameter Derivations

The coherence function has two kinds of parameters: the functional form (tanh, γ = 2/√Ncorr) which is derived from mean-field theory, and the scaling constants (A, a₀, Σ₀, R₀) which are derived from dimensional analysis with fundamental constants but show 3–12% errors against observations. Whether those errors reflect approximation limits or hidden calibration is an open question.

Badge labels on this page: Motivated Ansatz and Motivated Choice are sub-types of Speculative — indicating the parameter is physically motivated but not uniquely derived. Freeman's Law Re-expressed is a sub-type of Reparametrization. See badge taxonomy for the six official tiers.

The Complete Chain

1. γ = 2/√Ncorr

Motivated Ansatz

Sessions #64-65

The 1/√Ncorr scaling follows central-limit-theorem statistics for correlated ensembles. The factor of 2 is motivated by phase-space dimensionality arguments (6D to 3 effective) but is not rigorously derived — integrating out momenta introduces temperature- and mass-dependent factors, not a clean factor of 2. Best understood as a physically motivated ansatz.

2. tanh form

Motivated Choice

Session #66

tanh is a phenomenological choice from the Landau-universality family of sigmoid functions. Other sigmoids (logistic, erf) share the same qualitative properties and would produce indistinguishable physics near γ ≈ 1. The fractal coherence bridge failure (0/7 boundaries on 36 tests) is consistent with tanh being a generic sigmoid here, not a uniquely derived form.

Note on the Ising analogy: tanh arises in mean-field Ising models as m = tanh(βJzm) — but that tanh comes from the self-consistency equationm = tanh(βJz·m), where m feeds back into itself. C(ρ) has no such self-consistency loop: it is evaluated directly at the input ρ with no fixed-point iteration. The Ising tanh is derived; this tanh is chosen. These are structurally different justifications.

3. A = 4π/(βJ²GR₀²) ≈ 0.029

Jeans Criterion | 5% Agreement

Sessions #53, #66

βJ = λJeans / Rhalf is the dimensionless Jeans-length-to-galaxy-size ratio (Session 53). Empirically βJ ≈ 1.1 ± 0.2 across SPARC galaxies; βJ = 1.0 is the fiducial. From the Jeans criterion (ρcrit = V² / (GβJ²Rhalf²)) with R₀ = 8 kpc and the 4π factor from spherical surface-area integration (Session 66), A = 0.0294 vs empirical 0.028 — 5% agreement.

Symbol note (2026-04-24 correction): βJ is the Jeans ratio λJeans/Rhalf— an O(1) structural ratio, not the electromagnetic fine-structure constant αem ≈ 1/137. The formula was previously written with α, which invited that misread. With αem² ≈ 5×10−5, the formula yields A ≈ 550 (km/s)−2 — 20,000× too large. The formula only closes at 5% with βJ = O(1). No electromagnetic coupling is implied.

4. a₀ = cH₀/(2π) ≈ 1.08×10−10 m/s²

Dimensional Analysis

Sessions #87-88

The MOND acceleration scale a₀ = cH₀/(2π) follows from Synchronism's coherence function. Milgrom's observed: 1.20×10−10 m/s² (10% error).

This dimensional relation a₀ ∼ cH₀ has been noted since Milgrom (1983) and independently derived by multiple frameworks (McCulloch 2007, Verlinde 2017, Smolin 2017) with the same geometric factor. The quantities c and H₀ are dimensionally sufficient to produce an acceleration — cH₀ is not a Synchronism-specific derivation. Classified as dimensional analysis / reparametrization on the honest assessment page.

5. Σ₀ = cH₀/(4π²G) ≈ 110 M☉/pc²

Freeman's Law Re-expressed

Session #89

Freeman's surface density law (Freeman 1970): observed 124 M☉/pc², 12% error. The combination cH₀/G has dimensions of surface density, so this is dimensional bookkeeping — expressing Freeman's empirical value via cosmological constants, not deriving it from physics. Re-badged from “Validated” (2026-04-28): the 12% agreement is not sufficient to claim derivation of what is, in origin, an observational law.

6. R₀ = V²/(3a₀)

3% Error

Session #91

Characteristic radius from velocity and acceleration. 97% accuracy against observed values.

What's Notable

The derivation chain uses fundamental constants (c, G, α, H₀) plus one observable (Vflat). The functional form (tanh, γ) has zero free parameters. The scaling constants (A, a₀, Σ₀, R₀) show 3–12% agreement with observations.

Honest caveat: The 3–12% errors could reflect either (a) legitimate approximation limits in the dimensional analysis, or (b) implicit calibration through choice of Vflat as input. Distinguishing these requires independent derivation. The landing page describes the scaling constants as “fitted” — that may be the more conservative and accurate framing.

Next: Compression Action →Interactive Walkthrough

Prerequisites

Understanding these concepts first will help:

The Coherence FunctionC(ρ) = tanh(γ log(ρ/ρ_crit + 1))The γ Parameterγ = 2/√N_corr: why 2, why √NCritical Densityρ_crit = A V_flat²: the transition point

Related Concepts

MOND Unificationa₀ = cH₀/(2π) is emergent, not fundamentalEquation WalkthroughStep through parameter derivations interactively