problems / fekete-s2

Also in this folder: compute/

Walkthrough — a Table 3 replay, not a new bound

0. What was actually missing

Smale 7 is an algorithmic question: a polynomial-time machine that returns an NN-tuple within clog⁡Nc\log N of Emin⁡E_{\min}. That is not a one-night object. The finite object that can move is a better NN-point energy than a printed table, with points and a verifier.

The printed record used here is Ridgway–Cheviakov, Comput. Phys. Commun. 233 (2018), Table 3, fetched as the author PDF and checked with pdftotext. Rathbun–Ridgway, arXiv:2008.04880, refine the same N≤65N\le 65 list to 77 digits and do not claim new globals beyond the 2018 N=19,46N=19,46 improvements over Bergersen–Boal–Palffy-Muhoray 1994. Amore–Figueroa–Ramos, arXiv:2512.12416 (Dec 2025), map the landscape to N=160N=160 but do not print an Emin⁡(N)E_{\min}(N) table.

What was missing was not a new potential. It was an independent recomputation of those numbers, and a search at the NN where the 2018 paper itself reports slack (N=33N=33 saddle, N=19,46N=19,46 new globals, modest NN with nearby locals).

1. Named false starts

2. The useful failure

N=46N=46 is the useful failure. Ridgway–Cheviakov's new global (−249.4558479-249.4558479) is findable from a generalized spiral and from several rng starts. Many other rng starts land on their published local −249.454650-249.454650. Fibonacci stalls worse, at −249.44978-249.44978. The 2018 improvement over Bergersen is real and independently reproducible, and the old basin is still there. A third, lower basin did not appear.

That is the degree of freedom the night actually had: the 2018 paper already isolated the slack (N=19,46N=19,46 versus 1994; N=33N=33 as a hard saddle). Replaying those lines, and failing to undercut them, is the leftover.

3. The replay

Energy, after projecting to S2S^2:

E(X)=∑i<jlog⁡1∣xi−xj∣=−12∑i<jlog⁡(2(1−⟨xi,xj⟩)).E(X)=\sum_{i<j}\log\frac{1}{|x_i-x_j|} =-\frac12\sum_{i<j}\log\bigl(2(1-\langle x_i,x_j\rangle)\bigr).

compute/energy.py is the independent verifier. Closed forms:

E2=−log⁡2,E3=−32log⁡3,E4=3log⁡(3/8),E5=−4log⁡2−32log⁡3,E6=−9log⁡2.\begin{aligned} E_2&=-\log 2,\\ E_3&=-\tfrac32\log 3,\\ E_4&=3\log(3/8),\\ E_5&=-4\log 2-\tfrac32\log 3,\\ E_6&=-9\log 2. \end{aligned}

These match Table 3 to the printed 8 decimals, as do the pentagonal bipyramid (N=7N=7) and the regular icosahedron (N=12N=12).

Rathbun–Ridgway's Zenodo log.3.N.80 files were parsed (including the occasional 1/2 in the N=44N=44 algebraic file) and run through the same verifier. For every N=2N=2–6565, the recomputed EE equals the file's ener= to ∼10−13\sim 10^{-13} and equals Table 3 to the printed digit. That is the full replay.

Multi-start Riemannian descent with fixed seeds then recovered the same globals at N=7,8,9,10,14,19,24,32,33,46,48N=7,8,9,10,14,19,24,32,33,46,48. For N=24,32,48N=24,32,48 every seed — Fibonacci, spiral, and 32 rng — lands on the published energy. The table is not an artefact of one coordinate file.

4. What would have been a new bound

An explicit point set whose verifier energy is below the first Table 3 entry for that NN by more than rounding, with the points stored. That did not happen. The 77-digit Rathbun–Ridgway refinement of the same list is the sharper form of the same record. Smale 7 is the algorithmic question and is untouched.

5. How to replay

cd problems/fekete-s2/compute
sh run_all.sh

Expected: closed-form matches for N=2N=2–66, PASS from verify_replay.py, checkpoint energies agreeing with energy.py. The stored Table 3 extract is ridgway2018.json. The stored coordinate replay is replay_rathbun.json.