The Exact Rank Floor for Point-Span Tangent Absorption in Arbitrary Characteristic
Corrected version of a screened paper. Not peer reviewed. Screening record
Let X be a smooth projective integral d-fold over an algebraically closed field of arbitrary characteristic, let L be very ample, let m be at least one, and let Z be a nonempty finite reduced set whose point span in the complete L^m-embedding contains every tangent space at its supports. We prove the exact codimension-free floor h_Z(m), |Z| >= binom(d+m,d). An adapted finite projection to P^d transfers absorption to equality between the degree-m pieces of the radical ideal of the projected points and its symbolic square. The standard perfect-field derivative/p-th-root gap forces that piece to vanish. Simplex-lattice interpolation and characteristic-zero Bertini yield proper-span equality examples over C in every dimension and degree. No imperfect-field, singular, nonreduced, or equality-classification result is claimed.
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Cite this paper
Lluis Eriksson (2026). The Exact Rank Floor for Point-Span Tangent Absorption in Arbitrary Characteristic. AIRR.SCIENCE, ARR-2026-2MHNZRRJP49Y9SWP, v3. https://airr.science/papers/ARR-2026-2MHNZRRJP49Y9SWP/versions/v3/
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Revision statement
Minor revision. Makes exact replay JSON emission byte-stable across LF and CRLF platforms by forcing LF newlines; mathematical statements and proofs are unchanged.
Verification record
- Frontier-model screening
- Not assessed
- Source integrity
- Pass
- Bibliographic integrity
- Not assessed
- Reproducibility
- Partial
- Lean 4
- Not applicable
Recorded under ARR-VERIFY-1.0. AIRR verification and screening are not peer review.
AI assistance statement
OpenAI Codex assisted with proof discovery, adversarial proof auditing, primary-literature triage, exact replay code, drafting, PDF production, and AIRR packaging. The author remains responsible for the mathematical claims. A separate read-only Codex audit found no P0, and focused re-review scored this version 8.4/10 with uncertainty 0.6 after corrections. This is not human peer review or priority certification.
Frontier-model screening
Status: not_assessed. Any listed reports correspond to this exact version under ARR-SCREEN-1.0; no absent assessment is represented as a pass.
Model assessments and review context
- Distinct models
- 2
- Range
- 3.75–4.20
- Method
- bounded capability-weighted mean · exact version only
Limited evidence · 1/2 benchmark matches. This is an evidence description, not a probability of correctness.
One provider; shared blind spots possible; Fresh blinded review context not documented for every model; Benchmark match incomplete; Adverse reports or unresolved objections require editorial disposition
OpenAI · gpt-5.6-sol · High · unknown · review context: unknown4.20
Recommendation: Accept · Material objections: 0
This exact v3 PDF gives a convincing proof that point-span tangent absorption in a complete tensor-power embedding forces rank and cardinality at least binom(d+m,d) over any algebraically closed field. The adapted projection is finite and first-order étale at the selected points; absorption transfers equality of value and double-point kernels to their images in projective d-space, where the minimal-degree derivative/Frobenius argument rules out a nonzero degree-m vanishing form. The complex common-tangent construction genuinely realizes equality with proper point span. Secondary rank and Gauss-fibre refinements also check out. Novelty is plausible but deliberately narrow and not exhaustively certified.
- Correctness confidence
- The main chain—adapted finite projection, transfer of double vanishing, the perfect-field initial-degree gap, and injective degree-m evaluation—was checked step by step without finding a counterexample or missing hypothesis under the stated algebraically closed, smooth, reduced assumptions.
- Rigor
- The kernel criterion, projection lemma, Frobenius-radical alternative, cohomology restriction, and local common-tangent calculation are explicit and mutually consistent. The Bertini and literature-priority components remain conventionally sourced rather than independently re-proved.
- Novelty
- The manuscript responsibly limits novelty to combining classical projection and fattening tools into an exact universal floor plus proper-span extremizers. Targeted source checks support the classical boundaries, but no exhaustive priority search was performed.
- Significance
- An exact codimension-free lower bound valid in every characteristic, with sharp proper-span examples for every dimension and degree, is a clean and potentially reusable structural result, though it is not a broad classification theorem.
- Reproducibility
- All three standard-library replay programs were executed. Fresh outputs matched the three committed JSON witnesses byte-for-byte and covered exact interpolation ranks, common-tangent fixtures, and exhaustive stated finite-field support grids; they do not certify Bertini or the universal proof.
Strengths
- Theorem 1.1 isolates the exact logical chain: a center avoiding X, the selected tangent spaces, and selected secants yields a finite projection that is injective on Z with cotangent isomorphisms at every support.
- Lemma 3.1 handles characteristic p correctly: if every first partial of a minimal-degree homogeneous form vanishes, perfection gives a pth root and radicality lowers the degree, contradicting minimality.
- The consequence from equality in degree m to a zero value kernel is valid even when the minimal generator has lower degree, because a separate local-unit multiplier can be chosen at each support.
- Theorem 1.2 is not merely ambient saturation: simplex-lattice unisolvence and a smooth hypersurface with one prescribed common tangent hyperplane give equality while h0(X,L^m) is strictly larger.
- The replay suite states its finite scope accurately and reproduced all committed witnesses byte-for-byte in this execution.
Weaknesses
- The priority discussion is a selective bibliography rather than an exhaustive search for earlier formulations of the exact projection-plus-fattening synthesis.
- Proper-span sharpness is established over C at a deliberately large sufficient hypersurface degree; positive-characteristic sharpness, minimal degree, and equality classification are not supplied.
- The computational fixtures test finite ranks and local identities only; they provide no machine-checked verification of the projection, Bertini, or universal quantifiers.
Potential errors
None reported.
Strong novelty candidates
- The exact universal binomial rank floor for point-span tangent absorption over algebraically closed fields of arbitrary characteristic appears to be a strong novelty candidate as the stated synthesis of adapted projection and the symbolic-square initial-degree gap.
- The proper-span equality construction for every pair (d,m), with all selected tangent hyperplanes equal, is a concrete sharpness result not located in the targeted adjacent literature checks.
- The rank-sensitive first-jet and Gauss-fibre refinements are useful secondary consequences, although their ingredients are standard and their novelty was not independently certified.
Unresolved material objections
None reported.
arr:assessment:7893de27-fd6b-48ad-baaa-6c038422182b · prompt ARR-ASSESS-1.0 · runtime identity: OpenAI gpt-5.6-sol · reasoning effort: high · basis: operator verified ui · evidence SHA-256 e39832fe63664e06def63794bba6a7856fc12a5845e75117aadce46a1e574444 · response SHA-256 8e02cee914e7c5ee91b35bc53d60dc54997215cce4cfc4b76e645f2eb583af6d · canonical PDF SHA-256 af66e99f36e74234a53fa0ff3ba6895a84d14323b934e0faba252060079997ac
OpenAI · gpt-6-astra · High · unknown · review context: unknown3.75
Recommendation: Minor Revision · Material objections: 0
This exact nine-page v3 presents a convincing exact rank theorem in arbitrary characteristic. I checked the projection avoidance conditions, finiteness argument, minimal-degree fattening gap including the all-partials-zero case, rank transfer, complex sharpness construction, and secondary block/Gauss refinements. All three replay certificates were reproduced byte for byte. No unresolved objection capable of invalidating a main claim was found. Minor revisions should clarify the differential shorthand and the precise relation to known subspace-rank results. The contribution is a strong specialized synthesis, not a Millennium-problem result; broad priority remains unverified. This assessment is not an editorial decision.
- Correctness confidence
- Theorem 1.1 survives direct checks of the adapted projection, first-neighbourhood transfer and Frobenius/radical minimal-degree argument. Theorem 1.2 has a valid complex Bertini construction. No main-claim counterexample was found.
- Rigor
- The proof handles m=1,2, finite support and characteristic p explicitly. The local-unit step from equality in degree m to initial degree is essential and correctly supplied. Secondary Gauss and jet-block claims follow under the stated thresholds.
- Novelty
- The initial-degree gap and projection/interpolation ingredients are classical. Their use to obtain this exact simultaneous absorption rank theorem and proper-span examples is a credible synthesis; no exhaustive priority conclusion is justified.
- Significance
- A codimension-free sharp binomial bound in every characteristic is a useful structural theorem for a rigid incidence condition. Its scope is still specialized, and the complex extremizers do not classify equality or give optimal hypersurface degrees.
- Reproducibility
- All three supplied replays execute unmodified and match their respective stored JSON bytes. They cover 20 rational projection fixtures, six local extremizers and 149 finite-field supports, with explicit degree cutoffs; no global smoothness computation is claimed.
Strengths
- Lemma 3.1 (p. 4): double vanishing implies every homogeneous partial vanishes on Y. A nonzero derivative contradicts least degree; if all partials vanish, perfection gives F=G^p and radicality lowers the degree. The local-unit multiplication argument correctly extends the contradiction to equality of kernels in arbitrary degree m.
- Lemma 4.1 (p. 4): a general center avoids X, finitely many d-dimensional tangent spaces and finitely many secants. A positive-dimensional projective fibre would meet the center hyperplane, contradicting disjointness. Thus the projection is finite and has the required tangent isomorphisms.
- Theorem 1.1 (pp. 4-5): at zeros of F, the cotangent isomorphism transfers second-order vanishing from its pullback. Injective degree-m evaluation on Y then injects a binomial-dimensional evaluation subspace on Z, with no projective-normality assumption.
- Lemma 6.1 and Theorem 1.2 (pp. 5-6): the falling-factorial matrix is triangular with unit diagonal over C. With n>m, every section lifts uniquely; vanishing on Z forces divisibility by y, and y=-f/G belongs to m_p^2. This gives equality with a genuinely proper point span.
- Proposition 7.1 (p. 6): the system is base-point-free off Z, characteristic-zero Bertini applies there, and nonzero G(p) gives smoothness at every base point. Reducible positive-dimensional projective hypersurfaces would have intersecting components and be singular.
- Propositions 8.2-8.3 and Corollary 8.4 (p. 7): squared separators require m>=3; downward propagation forces r1>=d+1. Equality puts all supports in one Gauss fibre, yielding the stated alternative. The smooth-quadric polar-radical argument also works on geometric points in characteristic two.
- Section 10: fresh replay stdout records the 20 deletion-boundary fixtures, six local common-tangent fixtures, and exhaustive 7,15,127-support checks on P^1(F2), P^1(F3), P^2(F2). All three byte comparisons succeeded; no source-hashing failure occurred.
Weaknesses
- Section 5 writes d(s)_p=d(F)_q composed with d pi_p for sections of line bundles. Specify compatible local trivializations; because F(q)=0, the derivative at that zero is independent of the unit ambiguity. The current shorthand is repairable and does not invalidate the argument.
- The novelty comparison should engage explicitly with subspace rank, beyond Terracini and strong-base-locus terminology. Ballico defines rank by containment in a reduced point span and studies tangent-containing spaces: https://imar.ro/journals/Revue_Mathematique/pdfs/2013/4/4.pdf. This does not itself prove the present simultaneous theorem.
- Theorem 1.2 is proved over C only. The finite-field fattening replay checks the lower-bound mechanism and cannot extend the stated complex Bertini sharpness result to other characteristics.
- The local extremizer program uses F=f(t)+y and predetermined derivative-zero rows justified by squared factors. It does not certify smoothness of a global homogenization, and the manuscript correctly disclaims that stronger computation.
- The scripts inspect finite supports and fixed degree ranges, not arbitrary smooth varieties or adapted projections. Exact agreement with committed certificates strengthens reproducibility but supplies no independent universal proof or novelty certification.
- Bauer-Szemberg Lemma 2.4 was inspected as a classical differential precedent at https://arxiv.org/pdf/1308.4983. The exact Bocci-Chiantini Remark 2.2 was not retrieved in full; its attribution remains unchecked, although the manuscript gives a self-contained proof.
Potential errors
- No main-claim counterexample or unresolved proof gap was found. In characteristic two the quadric statement concerns injectivity on geometric points, not an isomorphism or separability of the Gauss map; the paper makes that distinction correctly.
Strong novelty candidates
- Theorem 1.1: transporting simultaneous tangent absorption by a finite projection adapted to the actual support converts a classical initial-degree gap into an exact, codimension-free evaluation-rank floor.
- Theorem 1.2: proper-span equality examples for every (d,m) over C show that the lower bound cannot be improved merely by excluding ambient spans; candidate synthesis rather than new interpolation machinery.
Unresolved material objections
None reported.
arr:assessment:c26a64a2-a5bf-4565-a5e3-9db3cf8fefb9 · prompt ARR-ASSESS-1.0 · runtime identity: OpenAI gpt-6-astra · reasoning effort: high · basis: operator verified ui · evidence SHA-256 41403f4daed52fef2850786d552ffbeca2e237796b98d49e308d5595f5cb7234 · response SHA-256 2ae5dfd9f4d828dee8eb39123233408018f7c52624aa231de2798fb7dd38c18d · canonical PDF SHA-256 af66e99f36e74234a53fa0ff3ba6895a84d14323b934e0faba252060079997ac
A model assessment is not peer review or a correctness certificate. AIRR preserves disagreement, exact-version provenance and later reassessments.
Editorial disclosure
Version v3 supersedes v2. Declared minor revision: Makes exact replay JSON emission byte-stable across LF and CRLF platforms by forcing LF newlines; mathematical statements and proofs are unchanged. All assessments apply only when explicitly rerun and recorded for this exact version.