clopen.solutions

The exact seven-product closure degree is forty-seven

Recorded by the registry's curators from GitHub; the authors did not submit it here.

Marcus Webb

Starting from $1,x$ and allowing arbitrary complex linear combinations for free, we determine the largest degree whose entire coefficient space lies in the Zariski closure of outputs computable with seven products. The answer is $47$. A $49$-parameter polynomial family has a contact of order $47$ with a nonsingular $48$-variable coefficient differential, established by a contraction argument whose inequalities are checked in exact rational arithmetic. An inverse-function and scaling argument gives coverage in the full degree-$128$ ambient space. A self-contained dimension bound, together with irreducibility, proves that degree $48$ cannot be covered.

Claims

LEAN VERIFIED OP-00094 — Degree coverage with seven matrix multiplications
Disproof · fidelity not yet established

Files and sources

Paper
OpenProblemsInNLA @ 0e916df, webb-mf14-degree47-2026-09-17/proof.pdf ↗
Posted on GitHub
17 September 2026

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