Finiteness of Central Configurations for Positive Masses

A Resolution of Smale's 6th Problem — T. Nagy (2026)

Theorem. For all N ≥ 3 and all positive masses, the number of central configurations modulo similarity is finite.
Łojasiewicz (compact variety) Complexify U = λ Branch point (Lemma B) F → ∞ ≠ λ (Lemma C) Contradiction

Figure 1 — The Degenerate Central Configuration at μ*

Equilateral triangle + center CC with the E-mode null eigenvector (arrows). The perturbation breaks S₃ symmetry.

Complex plane: branch points of F(z). Each color = one pair. Stars = φ-zeros, circles = ψ-zeros. Dashed circle = convergence radius ρ = 0.467.

Figure 2 — The Divergence Contradiction

|F(z)| along the radial path toward the nearest branch point (pair 1–4). F must equal λ = 7.004 everywhere, but diverges to ∞ at the branch point. This contradiction proves no curve of CCs can exist.

Figure 3 — Proof Mechanism: Why Positive Masses Matter

Monodromy: continuing F(z) = λ around a branch point z₀ flips signs of colliding pairs. The positivity sum Σ α/r = 0 with all terms > 0 is impossible.

With negative masses: terms with m_im_j < 0 allow cancellation. Roberts' counterexample (N=5) exploits this to create a curve of CCs.

Numerical Verification at the Degenerate CC

Mass ratio: μ* = (81 + 64√3)/249 ≈ 0.7705

Minimal polynomial: 249μ² − 162μ − 399 = 0

Null space dimension: 2 (E-mode of S₃)

Proportionality groups: 6/6 independent

Private branch points: 12/12

S₃-equivariant resultant: Res = −4|β|⁴ = −238,079 ≠ 0

PairNearest |z₀|Private?
(1,2)1.275
(1,3)1.275
(1,4)0.467✓ nearest
(2,3)1.275
(2,4)0.724
(3,4)1.000

Key Innovation

Previous proofs (Hampton–Moeckel for N=4, Albouy–Kaloshin for N=5) use algebraic elimination and BKK theory — methods that become intractable for N ≥ 6.

This proof works by complexifying the identity U = λ. In the complex plane, each pair (i,j) creates branch-point singularities where the complexified distance r_ij(z) vanishes. The Newtonian potential's pairwise structure + positive masses prevent these singularities from canceling — yielding a divergence contradiction that works uniformly for all N.

The tools are standard complex analysis: identity theorem, monodromy of √, Liouville's theorem. No Morse theory, no IFT, no equivariant analysis required.