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Golden Jones Matching

Abstract

The golden square is the first nonintegral low Jones value and the Fibonacci dimension.

Theorem 1.1 (The golden square is the first nonintegral low Jones value).

Proof. Machine-checked in Lean as D5/S3/Observer/GoldenCoding/GoldenJonesMatching.golden_jones_matching (✓ std3). ∎

Source. Repository-derived.

Commentary.

For J(n)=4 cos^2(pi/n), the four explicit values at n=3,4,5,6 are 1, 2, phi^2, and 3. The central identity uses the repository’s pentagon cosine theorem rather than reproving the special value.

The radical identity phi^2=(3+sqrt(5))/2 yields both 2<phi^2<3 and the sharper enclosure 2.6<phi^2<2.62. Irrationality of phi then shows that J(5) is not an integer, while the only earlier indices n>=3 are n=3 and n=4 and have explicit integer witnesses.

The source also describes the self-dual Fibonacci fusion rule. Because the source supplies no category, tensor product, unit, or dimension map, the formal statement records its exact decategorified numerical consequence: every positive d satisfying d^2=1+d equals phi and has squared dimension phi^2.

References