ramanujan-challenge/docs/proofs/PROBLEM_28_COMPLETE_PROOF.md
Codex 437b439c6c feat(p28): close exact Ramanujan 2.8 limit
Portable proof handoff intended for verified mirror base 1229ab9e61bee936cb1a29c0693ee56922d2d908.
2026-07-31 14:30:10 +09:00

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# Problem 2.8 — Exact Hypergeometric Tail Closure
**Status:** PROVED
**Date:** July 2026
For every official column \(j=1,2,3,4\), the authoritative recurrence
satisfies
\[
\lim_{N\to\infty}\frac{P_{N,j}}{Q_{N,j}}
=\frac{\sqrt{10005}}{\pi}.
\]
Equivalently, in the orientation requested by Ramanujan Challenge
Problem 2.8,
\[
\boxed{\displaystyle
\lim_{N\to\infty}\frac{Q_{N,j}}{P_{N,j}}
=\frac{\pi}{\sqrt{10005}}}.
\]
## Exact closure
The proof closes the former connection-functional gap through:
1. an exact nonterminating \({}_4F_3\) tail with
\(M_Nk_{N+1}=k_N\);
2. a rank-one discrete-valuation argument giving the all-\(N\)
Padé divisibility pattern;
3. an exact terminating adjoint \({}_4F_3\) formula for the denominator;
4. positivity at \(z_0=-1/53360^3\) and a fixed-point Cauchy bound with
\[
\beta=
\frac{3125}{1307443596565949700399927}
<4\cdot10^{-19};
\]
5. the Chudnovsky CM value
\(\Phi(x_0)=\sqrt{10005}/\pi\);
6. an exact Rouché separation of the characteristic quartic, a positive
denominator lower bound, and the cyclic-frame argument transferring the
first-column result to all four columns.
The proof is structural and does not infer equality from the earlier
\(10^{-1052}\) numerical enclosure.
## Authoritative artifacts
- `docs/proofs/PROBLEM_28_PROOF.tex`
- `docs/proofs/PROBLEM_28_PROOF.pdf`
- `experiments/ramanujan_28/submission/`
- `experiments/ramanujan_28/submission/ramanujan_challenge_problem_2_8.zip`
The primary Wolfram Language certificate contains 22 exact symbolic checks
plus a consolidated PASS conclusion. Dependency-free Python checks verify
the rank-one algebra, the Rouché inequality, and the convergence constants.
Independent SageMath certificates provide secondary exact cross-checks.
## Release verification
- Independent adversarial proof audit: **PASS**
- Wolfram exact checks: **22/22 PASS**
- Python exact checks: **PASS**
- LaTeX build: **PASS**, zero warnings
- PDF visual inspection: **PASS**, all 10 pages
- Clean ZIP extraction and PDF rebuild: **PASS**
SHA-256:
```text
PDF a70c50287b24d13bdb113bcdbf87011dcbd698fdd4a7566ede5a8b37aeb8c2b9
ZIP 60b9d60808af129a339064e72b2ad5bd8ff9bc933c3905cf8faf821316cab91d
```