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Central Configuration


A central configuration in the n-body problem is defined for bodies of positive masses m_1,...,m_n at positions q_1,...,q_n. Let c be their center of mass and let U(q)=sum_(i<j)m_im_j/||q_i-q_j|| be the Newtonian potential. A collision-free configuration q is a central configuration if there is a number lambda such that

 del _(q_i)U(q)+lambdam_i(q_i-c)=0 for i=1,...,n.

Central configurations generate homographic motions of the bodies. In the plane, each one generates a relative equilibrium that rotates rigidly about the center of mass. They are therefore normally considered up to similarity.

Tomar (2026a) proved that, for every choice of four positive masses and every cyclic ordering of the bodies, there is exactly one strictly convex planar central configuration with that ordering, up to similarity. This settles the Simó-Yoccoz conjecture. The proof uses interval arithmetic; the computation was repeated with an independently written program, and the uniqueness theorem and its computation were formalized in Lean and checked by its kernel.

Tomar (2026a) states that generative AI tools were used to find and prove the results and write both verification programs and the Lean formalization.

Tomar (2026b) reported that, for every choice of five positive masses, the planar five-body problem has finitely many central configurations up to similarity. This addresses the planar five-body case of problem 6 in Smale's problems, not the problem for an arbitrary number of bodies. For masses proportional to a permutation of (1,4,4,4,4) and (1,1,4,4,4), Tomar (2026b) reports exactly 306 and 294 central configurations, respectively, up to orientation-preserving similarity. The certificates and Lean formalization have not been independently checked here. Tomar (2026b) states that generative AI was used to find and prove the results and write the verification programs and formalization.

The spatial five-body problem has a separate finiteness question. Liu and Liu (2026) reported that, for any fixed five strictly positive masses, there are only finitely many collision-free Newtonian central configurations whose affine hull has dimension exactly three, up to similarity. Body labels are retained, and the similarities allow translations, orthogonal transformations including reflections, and positive scaling. The claim concerns this three-dimensional class and does not establish finiteness for planar configurations or for every spatial five-body configuration.

Liu and Liu (2026) report using Codex for mathematical proof analysis. Their finiteness claim remains subject to independent verification.


See also

Center of Mass, n-Body Problem, Similarity, Smale's Problems, Three-Body Problem

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References

Liu, K. and Liu, Y. "Finiteness of Dziobek Central Configurations in the Newtonian Five-Body Problem." 23 Oct 2026. https://arxiv.org/abs/2610.32751.Tomar, T. S. "Finiteness of Planar Central Configurations of Five Bodies for All Positive Masses." 9 Oct 2026b. https://arxiv.org/abs/2610.13100.Tomar, T. S. "Uniqueness of Four-Body Convex Central Configurations for All Masses." 28 Sep 2026a. https://arxiv.org/abs/2609.35632.

Cite this as:

Weisstein, Eric W. "Central Configuration." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/CentralConfiguration.html

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