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Cohomology classes of complex approximable algebras

T0 review · reviewed 2026-05-24 · grok-4.3

Pith's one-line read Over the complex numbers, the infinite Weil divisor associated to an approximable graded algebra has finite cohomology class.

desk verdict Over ℂ the infinite Weil divisor tied to approximable graded algebras has finite cohomology class, as a direct extension of the author's earlier association result. read the letter →

arxiv 2103.07120 v3 pith:23WX3WVR submitted 2021-03-12 math.AG

classification math.AG
keywords approximablegradedalgebrasinfiniteWeildivisorscohomologyclassescomplexalgebraicgeometrybiglinebundlesFujitatheoremarithmetic
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

Huayi Chen introduced approximable graded algebras to establish a Fujita-type theorem in arithmetic geometry and asked whether every such algebra arises as the graded ring of a big line bundle on a projective variety. Prior work showed this is not always true but established that every approximable graded algebra corresponds to an infinite Weil divisor. This paper proves that, when the base field is the complex numbers, the associated infinite Weil divisor must have finite cohomology class.

What carries the argument

The correspondence, established in prior work, that associates each approximable graded algebra to an infinite Weil divisor and thereby reduces the question to the finiteness of its cohomology class.

What would settle it

An explicit example of an approximable graded algebra defined over the complex numbers whose associated infinite Weil divisor has infinite-dimensional cohomology.

Watch

Extended reading notes

Core claim

The paper proves that over the complex numbers the infinite Weil divisor associated to any approximable graded algebra has finite cohomology class.

Load-bearing premise

The prior association between approximable graded algebras and infinite Weil divisors continues to hold when the base field is restricted to the complex numbers.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

0 major / 0 minor

Summary. The paper shows that over the complex numbers, the infinite Weil divisor associated to an approximable graded algebra necessarily has finite cohomology class. This builds on the author's prior result that any approximable graded algebra is associated to an infinite Weil divisor (following Chen's introduction of the notion for an arithmetic Fujita-type theorem).

Significance. If the result holds, it establishes a finiteness property for the cohomology class in the complex case, providing a concrete restriction that may help relate the arithmetic constructions to complex geometry. The manuscript relies on the prior independent association without introducing new free parameters or ad-hoc axioms.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their report. The summary correctly describes the paper's contribution: over the complex numbers, the infinite Weil divisor associated to an approximable graded algebra has finite cohomology class, building on the prior association result. The recommendation is listed as uncertain, but the major comments section contains no specific points or concerns. We therefore provide no point-by-point responses below.

Circularity Check

0 steps flagged · score 2.0 of 10

Minor self-citation to prior association; central claim independent

full rationale

The paper's derivation relies on the author's prior result associating approximable graded algebras to infinite Weil divisors, but the new claim (finite cohomology class over C) adds independent content via restriction to the complex numbers and does not reduce any quantity to a fitted input, self-definition, or self-citation chain within this manuscript. No equations or steps in the provided abstract or description exhibit the enumerated circular patterns; the prior work supplies external support rather than forcing the result by construction.

Assumptions & free parameters 0 free parameters · 2 assumptions · 0 invented entities

Review based on abstract only; no access to full definitions, lemmas, or sections that would list free parameters or axioms.

assumptions (2)
  • domain assumption Definition of approximable graded algebra (Chen)
    Central object of study introduced in cited prior work.
  • domain assumption Association of such algebras to infinite Weil divisors (prior paper)
    Load-bearing link from author's earlier result.

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Cite this review

Pith. "Pith review of Cohomology classes of complex approximable algebras." pith.science (2026). https://pith.science/paper/23WX3WVR

@misc{pith2026210307120,
  author       = {Pith},
  title        = {Pith review of: Cohomology classes of complex approximable algebras},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/23WX3WVR}},
  note         = {Machine review of arXiv:2103.07120}
}
read the original abstract

Huayi Chen introduces the notion of an approximable graded algebra, which he uses to prove a Fujita-type theorem in the arithmetic setting, and asked if any such algebra is the graded ring of a big line bundle on a projective variety. This was proved to be false in a previous paper of the author's, who subsequently proved that any such algebra is associated to an infinite Weil divisor. In this paper, we show that over the complex numbers, this infinite Weil divisor necessarily has finite cohomology class.

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Reviewed May 24, 2026 · model on record in the stance chip above.