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CATALOGUE 034

Log abundance and effective Iitaka fibrations

From a first section to a good model, and from a good model to a uniform Iitaka degree. Follow the claims of 14 manuscripts and the results their arguments use.

14manuscript summaries23selected connections14proof overviews

This is a reading map of the manuscripts’ claims and uses of cited results. The arrows record selected source-to-use connections; they are not a complete dependency graph or a certification of the proofs.

All 14 manuscripts, in official order

The summaries give the principal scope, not every technical hypothesis. Follow the theorem reference for the full statement. A uniform degree here is an existence statement unless a manuscript explicitly gives a numerical value.

Page counts include references. On narrow screens, scroll the table sideways.

Catalogue 034 · Pinned source snapshot checked on 8 October 2026
#Manuscript and overviewPrincipal claimRole and available overview

Three strands of the argument

These are reading groups for this guide. The numbered manuscript inventory above retains the official catalogue order. Short names used in diagrams are paired with the full titles there.

1. Nonvanishing and abundance: from a first section to generation

Log Abundance supplies all-dimensional good models. Alongside it, the fourfold papers separate nonvanishing from lifting. Schnell is an application of the geometry of the resulting good model.

Metrics and independent Log Abundance tools feed fourfold nonvanishing, which combines with lifting to give fourfold abundance. Separately, Log Abundance good models feed Schnell.
Solid arrows supply theorems or corollaries; dashed arrows supply auxiliary results. The two Log Abundance boxes denote different results in the same paper. Underlined arrow labels open the connection details; paper names open their proof overviews.
Arrow links open the result and its use below; paper names open the articles. Tap the figure to enlarge it.Open figure ↗TeX source ↓

1. Metrics extend boundary sections; nonzero sections need another input

Fourfold nonvanishing uses Minimal metrics, Theorems 1.1–1.2, for zero-Lelong metrics and interior injectivity on the endpoint residual bundles. These supply surjectivity of restriction. Three-dimensional semi-dlt abundance and descent separately produce a nonzero section on the whole boundary; combining the two steps gives nonvanishing upstairs.

Fourfold nonvanishing · Proof overview →

2. The remaining nonvanishing argument imports Log Abundance tools

The moving-jet argument imports Log Abundance, Lemmas 7.1–7.5, to control centres, degrees and covers. Theorem 9.1 then rules out coexistence of the constructed jets, flag and movable curve by Frobenius comparison. These are auxiliary inputs, rather than an application of Log Abundance’s abundance main theorem.

Fourfold nonvanishing · Proof overview →Log Abundance · Proof overview →

3. Combine nonvanishing with abundance after nonvanishing

Supported lifting, Theorem 1.2, proves fourfold semiampleness assuming nonnegative Kodaira dimension. Fourfold nonvanishing, Corollary 1.2, supplies the first section, giving Supported lifting, Corollary 1.4. A separate input to its conditional Theorem 1.3 is FN Lemma 8.1: rational linear algebra converting an effective real presentation to a rational one. The two uses must be distinguished.

Supported lifting · Proof overview →

4. Once a good model is supplied, Schnell finishes by intersection theory

Log Abundance, Corollary 11.2, supplies a model with semiample canonical divisor and an effective exceptional comparison. Schnell transfers sections to bound the Kodaira dimension, then uses the mixed intersections of Lemma 2.3 for the remaining inequality. Model existence is the imported input; the subsequent intersection argument is carried out in Schnell.

Schnell · Proof overview →

2. Effectivity: from existence of sections to a uniform degree

Good models alone do not bound the degree uniformly. The arguments separately control generic-fibre indices, moduli denominators on the base and degrees of finite covers. The diagram shows the six papers addressing these tasks and an input from Log Abundance.

Relative denominators feed Fourfold Iitaka. Its chain lemmas and Stein degrees feed Uniform Iitaka. Normal lc indices feed Log Iitaka and slc indices; product covers in Log Iitaka also feed slc indices.
The dashed arrow from Fourfold Iitaka to Uniform Iitaka uses chain lemmas stated in arbitrary dimension, not the fourfold main theorem. The text below adds the other applications of Log Abundance and Supported lifting.
Arrow links open the result and its use below; paper names open the articles. Tap the figure to enlarge it.Open figure ↗TeX source ↓

1. Separate qualitative good models from uniform denominators

In Fourfold Iitaka, Log Abundance supplies nonvanishing from pseudo-effectivity and Supported lifting makes the nef adjoint semiample after nonvanishing. Relative denominators, Theorem 1.1 and Proposition 6.1, control relative denominators and complete systems on a big base uniformly. The qualitative step supplies the fibration; the effective step captures its function field in a uniform degree.

Fourfold Iitaka · Proof overview →Relative denominators · Proof overview →

2. Induct on normal lc indices and Iitaka degrees together

Uniform Iitaka combines Log Abundance good models with Stein degree, Theorem 1.1, bounding constant-field extensions of boundary components and hence norm descent. Arbitrary-dimensional chain lemmas from Fourfold Iitaka lead from covering families to estimates on leaves. The output is a uniform complete system generating the full Iitaka field, not just an image of the right dimension.

Uniform Iitaka · Proof overview →Stein degree · Proof overview →

3. Use normal indices on the generic fibre to obtain log Iitaka effectivity

Log Iitaka applies Uniform Iitaka, Theorem 1.2, to the generic fibre, fixing a uniform trivializing multiple and an exact pullback presentation. Log Abundance supplies the semiample model, while Stein degree controls finite extensions in the residue induction. The finite rational coefficient set of the log Iitaka main theorem should be distinguished from the rational DCC coefficient scope of the normal lc index theorem.

Log Iitaka · Proof overview →

4. For slc pairs, glue normalization trivializations across the conductor

slc indices applies the normal lc index theorem on normalization components, but descent to the original slc pair needs more. Product covers and stability under further covers from Log Iitaka, the rational-image lemma from Uniform Iitaka, and Log Abundance good models enter the character bounds. Residues and cycles must then be made compatible. The slc paper itself supplies the final conductor gluing.

slc indices · Proof overview →

3. Kähler: retain dimension, singularities and premises

Conditional all-dimensional lc abundance, conditional klt fourfold models, and klt fourfold abundance after nonvanishing have different scopes. Dimension-free auxiliary lemmas are drawn separately from the main theorems of the papers containing them.

Kähler abundance after nonvanishing supplies Assumption 2.4 of conditional fourfold models. Log Abundance supplies the projective anchor for all-dimensional Kähler abundance; dimension-free lemmas in the conditional fourfold paper supply strata adjunction and strict comparison.
Dotted arrows denote explicit premises. The model theorem at lower left retains Assumptions 2.2–2.4; all-dimensional lc abundance at lower right retains Assumption 1.1. The horizontal dashed arrow imports only the strata lemmas.
Arrow links open the result and its use below; paper names open the articles. Tap the figure to enlarge it.Open figure ↗TeX source ↓

1. In dimension four, separate MMP, nonvanishing and subsequent abundance

Conditional Kähler models proves nonvanishing at the specified nef MMP endpoint, then invokes Kähler after nonvanishing, Theorem 1.1, for semiampleness. This is Assumption 2.4. Orbifold subadditivity (Assumption 2.2) and the specified MMP (Assumption 2.3) remain necessary; the after-nonvanishing theorem alone does not supply all premises.

Conditional Kähler models · Proof overview →Kähler after nonvanishing · Proof overview →

2. For all-dimensional lc abundance, connect a projective anchor to analytic induction

Kähler abundance, Proposition 2.10, uses the full Log Abundance induction for projective good models and effective exceptional comparison. The argument then splits into a positive-dimensional fibration case and a simple case of algebraic dimension zero. Theorem 6.1 in the latter gives meromorphic nonvanishing, not directly a holomorphic section. Signed-boundary rigidity and lower-dimensional induction return to generation of the original nef adjoint. Assumption 1.1 remains in the main theorem.

Kähler abundance · Proof overview →Kähler abundance · Proof overview →

3. The inputs extending beyond dimension four are specified lemmas

Conditional Kähler models, Lemmas 7.16–7.17, give dimension-free strata adjunction and strict comparison, used in Kähler abundance, Theorem 3.13. Torsion-freeness in Kähler after nonvanishing, Lemma 7.1, is another input: Kähler abundance, Lemma 4.3, uses it to pass from residue matching to section extension. Neither connection applies a fourfold main theorem in arbitrary dimension.

Kähler abundance · Proof overview →Kähler after nonvanishing · Proof overview →

Follow a result into its application

The diagrams select principal routes. This explorer includes the other recorded connections. Choose a manuscript and direction, or follow an arrow above to open its result-level record. The initial view shows the three inputs recorded for Log Iitaka.

23 selected connections

  1. Auxiliary result

    Converts a real effective presentation to a rational one using finite rational linear constraints. This linear-algebra lemma uses no nonvanishing theorem and is distinct from the input to Corollary 1.4.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  2. Auxiliary result

    Supplies actual adjunction on normalized strata and strict discrepancy comparison over the exceptional locus. Both lemmas are dimension-free; the fourfold main theorem is not applied in all dimensions.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  3. Auxiliary result

    Uses torsion-freeness of the first higher direct image when the pair is klt off its floor and an actual positive adjoint multiple is pulled back from the base, to turn generic-fibre residue matching into extension of restricted sections.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  4. Auxiliary result

    Independent tools controlling centre degrees, moving multiplicities, slices, and finite covers of a fixed branch complement.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  5. Auxiliary result

    Supplies the rational-image property of boundary-free nonabelian factors for the Hodge-rank theorem. The source lemma itself uses Log Abundance nonvanishing.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  6. Auxiliary result

    Uses a quasi-étale product cover and stability under further covers to control the character on the volume form factor by factor.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  7. Theorem input

    Supplies a good minimal model, semiampleness, and effective exceptional comparison for a pseudo-effective canonical divisor.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  8. Theorem input

    Identifies endpoint residual bundles with positive rational multiples of nef klt adjoints, supplying zero-Lelong metrics and interior injectivity. A nonzero section on the whole boundary additionally uses three-dimensional semi-dlt abundance and descent.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  9. Auxiliary result

    Rules out coexistence of the fixed jets, flag, and movable curve constructed in dimension four. This input is the independent Frobenius theorem, not Log Abundance’s abundance theorem.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  10. Input to a corollary

    Provides the first section on the original variety; combined with the independent Theorem 1.2 to obtain fourfold log abundance.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  11. Theorem input

    Makes a nef adjoint with known nonvanishing semiample, in the model comparison preserving rounded section spaces in every degree.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  12. Theorem input

    Controls moduli denominators and supplies a uniform degree generating the full field of a positive-dimensional big base.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  13. Theorem input

    Provides the qualitative first section from pseudo-effectivity. Uniform degree comes later from index and relative denominator arguments.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  14. Theorem input

    Supplies all-dimensional projective lc good models, including nonvanishing and semiampleness on the model.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  15. Theorem input

    Bounds the Stein degree of a coefficient-one component, controlling the index when a principal divisor descends by a field norm.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  16. Auxiliary result

    Constructs a rational fibration from chains of covering families and bounds section orders and degrees on its leaves. Uses the arbitrary-dimensional chain lemmas, rather than the fourfold main theorem.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  17. Theorem input

    Supplies a uniform trivializing degree on the generic fibre, fixing an exact pullback presentation.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  18. Theorem input

    Bounds the field extension from the Stein curve of a boundary component in the residue induction.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  19. Theorem input

    Passes from nonnegative Iitaka dimension to a good model, where the effective-degree argument uses the semiample fibration.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  20. Theorem input

    Trivializes all lc normalization components in one even degree. The receiving paper adds conductor gluing.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  21. Theorem input

    Supplies good models of perturbed projective klt pairs in the Hodge-rank argument.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  22. Theorem input

    Uses Log Abundance’s full induction under the stated logarithmic subadditivity assumption to supply projective good models and effective exceptional comparison.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection
  23. Explicit premise

    Gives semiampleness once nonvanishing is obtained for the nef Kähler klt fourfold adjoint. The other two premises remain separate.

    Source overview →Receiving overview →Input statement and the receiving connection compared; the complete input proof is not verified.Link to this connection

Arrows run from the supplied result to its use. Numbers 01–14 are positions within catalogue 034. Citations open the manuscript on GitHub.

Read dependencies at the level of results: Fourfold nonvanishing uses Log Abundance’s independent geometric tools and Frobenius theorem. Its abundance main theorem is not that input. In Supported lifting, fourfold nonvanishing enters Corollary 1.4; Theorem 1.2 already assumes a first section. These distinctions matter when tracing apparent back-and-forth citations.

View all 23 recorded connections as a table
Selected direct inputs within catalogue 034
Source resultUsed inInput and roleEditorial check
Fourfold nonvanishing by minimal metrics and moving jetsLemma 8.1 · p. 35 Supported lifting: Theorem 1.3, proof · p. 27 Converts a real effective presentation to a rational one using finite rational linear constraints. This linear-algebra lemma uses no nonvanishing theorem and is distinct from the input to Corollary 1.4.Input statement and the receiving connection compared; the complete input proof is not verified.
Conditional good minimal models for compact Kähler fourfoldsLemmas 7.16–7.17 · pp. 58–60 Kähler abundance: Theorem 3.13, proof · pp. 29–30 Supplies actual adjunction on normalized strata and strict discrepancy comparison over the exceptional locus. Both lemmas are dimension-free; the fourfold main theorem is not applied in all dimensions.Input statement and the receiving connection compared; the complete input proof is not verified.
Abundance after nonvanishing for compact Kähler fourfoldsLemma 7.1 · pp. 51–52 Kähler abundance: Lemma 4.3, proof · p. 74 Uses torsion-freeness of the first higher direct image when the pair is klt off its floor and an actual positive adjoint multiple is pulled back from the base, to turn generic-fibre residue matching into extension of restricted sections.Input statement and the receiving connection compared; the complete input proof is not verified.
Log abundance in characteristic zeroLemmas 7.1–7.5 · pp. 45–52 Fourfold nonvanishing: §3 / Proposition 6.4 · pp. 8–12, 24 Independent tools controlling centre degrees, moving multiplicities, slices, and finite covers of a fixed branch complement.Input statement and the receiving connection compared; the complete input proof is not verified.
Uniform Pluricanonical Iitaka FibrationsLemma 5.2 · pp. 21–22 slc indices: Lemma 6.6 · pp. 32–34 Supplies the rational-image property of boundary-free nonabelian factors for the Hodge-rank theorem. The source lemma itself uses Log Abundance nonvanishing.Input statement and the receiving connection compared; the complete input proof is not verified.
Uniform log Iitaka fibrations and bounded moduli denominatorsProposition 5.1 / Lemmas 5.2–5.3 · pp. 12–13 slc indices: Input 6.3 / Lemma 6.4 · pp. 30–32 Uses a quasi-étale product cover and stability under further covers to control the character on the volume form factor by factor.Input statement and the receiving connection compared; the complete input proof is not verified.
Log abundance in characteristic zeroCorollary 11.2 · pp. 73–74 Schnell: Theorem 3.1 / §4.1 · pp. 7–8 Supplies a good minimal model, semiampleness, and effective exceptional comparison for a pseudo-effective canonical divisor.Input statement and the receiving connection compared; the complete input proof is not verified.
Minimal metrics and interior injectivity for nef adjointsTheorems 1.1–1.2 · pp. 1–2 Fourfold nonvanishing: Theorems 4.1–4.2 / §5 · pp. 13–20 Identifies endpoint residual bundles with positive rational multiples of nef klt adjoints, supplying zero-Lelong metrics and interior injectivity. A nonzero section on the whole boundary additionally uses three-dimensional semi-dlt abundance and descent.Input statement and the receiving connection compared; the complete input proof is not verified.
Log abundance in characteristic zeroTheorem 9.1 · pp. 62–69 Fourfold nonvanishing: Theorem 7.1 / §7 · pp. 30–34 Rules out coexistence of the fixed jets, flag, and movable curve constructed in dimension four. This input is the independent Frobenius theorem, not Log Abundance’s abundance theorem.Input statement and the receiving connection compared; the complete input proof is not verified.
Fourfold nonvanishing by minimal metrics and moving jetsCorollary 1.2 · p. 2 Supported lifting: Corollary 1.4, proof · p. 29 Provides the first section on the original variety; combined with the independent Theorem 1.2 to obtain fourfold log abundance.Input statement and the receiving connection compared; the complete input proof is not verified.
Lifting sections from the reduced support of an adjointTheorem 1.2 · p. 2 Fourfold Iitaka: Theorem 2.1 / Proposition 2.2 · pp. 6–7 Makes a nef adjoint with known nonvanishing semiample, in the model comparison preserving rounded section spaces in every degree.Input statement and the receiving connection compared; the complete input proof is not verified.
Relative denominators and effective systems for log Calabi-Yau fibrationsTheorem 1.1 / Proposition 6.1 · pp. 2, 15 Fourfold Iitaka: §3 / §10 · pp. 8, 48–49 Controls moduli denominators and supplies a uniform degree generating the full field of a positive-dimensional big base.Input statement and the receiving connection compared; the complete input proof is not verified.
Log abundance in characteristic zeroTheorems 1.1, 11.1 / Lemma 2.2 · pp. 2, 73, 8 Fourfold Iitaka: §10 · p. 48 Provides the qualitative first section from pseudo-effectivity. Uniform degree comes later from index and relative denominator arguments.Input statement and the receiving connection compared; the complete input proof is not verified.
Log abundance in characteristic zeroTheorem 11.1 · p. 73 Uniform Iitaka: Theorem 2.1 · p. 4 Supplies all-dimensional projective lc good models, including nonvanishing and semiampleness on the model.Input statement and the receiving connection compared; the complete input proof is not verified.
Arithmetic Stein-degree bounds for log Calabi–Yau pairsTheorem 1.1 · p. 1 Uniform Iitaka: Proposition 3.2, proof · pp. 7–8 Bounds the Stein degree of a coefficient-one component, controlling the index when a principal divisor descends by a field norm.Input statement and the receiving connection compared; the complete input proof is not verified.
Uniform effective log Iitaka fibrations for fourfoldsLemma 5.1 / Corollary 5.2 / Lemma 5.4 · pp. 18, 20–21 Uniform Iitaka: Lemma 6.2 · pp. 24–25 Constructs a rational fibration from chains of covering families and bounds section orders and degrees on its leaves. Uses the arbitrary-dimensional chain lemmas, rather than the fourfold main theorem.Input statement and the receiving connection compared; the complete input proof is not verified.
Uniform Pluricanonical Iitaka FibrationsTheorem 1.2 · p. 2 Log Iitaka: Theorem 2.1 / Proposition 7.1 · pp. 5, 23–24 Supplies a uniform trivializing degree on the generic fibre, fixing an exact pullback presentation.Input statement and the receiving connection compared; the complete input proof is not verified.
Arithmetic Stein-degree bounds for log Calabi–Yau pairsTheorem 1.1 · p. 1 Log Iitaka: Theorem 2.3 / Lemma 4.6 · pp. 5, 10–11 Bounds the field extension from the Stein curve of a boundary component in the residue induction.Input statement and the receiving connection compared; the complete input proof is not verified.
Log abundance in characteristic zeroTheorem 11.1 · p. 73 Log Iitaka: Theorem 2.2 / §8 · pp. 5, 29 Passes from nonnegative Iitaka dimension to a good model, where the effective-degree argument uses the semiample fibration.Input statement and the receiving connection compared; the complete input proof is not verified.
Uniform Pluricanonical Iitaka FibrationsTheorem 1.2 · p. 2 slc indices: Theorem 2.2 / §7.3 · pp. 5, 37 Trivializes all lc normalization components in one even degree. The receiving paper adds conductor gluing.Input statement and the receiving connection compared; the complete input proof is not verified.
Log abundance in characteristic zeroTheorem 11.1 · p. 73 slc indices: Theorem 2.3 / Lemma 5.6 · pp. 5, 20–21 Supplies good models of perturbed projective klt pairs in the Hodge-rank argument.Input statement and the receiving connection compared; the complete input proof is not verified.
Log abundance in characteristic zeroProposition 2.5 / Theorem 9.6 / §10 · pp. 9–12, 69–73 Kähler abundance: Proposition 2.10 · p. 12 Uses Log Abundance’s full induction under the stated logarithmic subadditivity assumption to supply projective good models and effective exceptional comparison.Input statement and the receiving connection compared; the complete input proof is not verified.
Abundance after nonvanishing for compact Kähler fourfoldsTheorem 1.1 · p. 3 Conditional Kähler models: Assumption 2.4 · p. 9 Gives semiampleness once nonvanishing is obtained for the nef Kähler klt fourfold adjoint. The other two premises remain separate.Input statement and the receiving connection compared; the complete input proof is not verified.

Inputs from outside catalogue 034

033 → Log Abundance: subadditivity

Log Abundance’s Lemma 6.1 uses Corollary 6.2 of the orbifold Iitaka manuscript in catalogue 033, in its zero-boundary projective case. The Log Abundance overview also explains how the existing Hacon–Popa–Schnell result supplies this particular application.

See the statements and application in Log Abundance →

033 / 056 → conditional Kähler models

The receiving manuscript identifies orbifold subadditivity and the specified Kähler MMP as Assumptions 2.2–2.3. Together with abundance after nonvanishing from 034, they form its three premises. The companion statements and selected application conditions are compared in the conditional Kähler overview. The complete proofs of the premises have not been independently verified.

Assumptions 2.2–2.4 · pp. 7–9 ↗ Read the conditional overview →

Established inputs such as Hashizume’s reduction, gluing, lower-dimensional abundance, and effective birationality are not exhaustively mapped here. The individual articles identify their selected external inputs separately. The all-dimensional Kähler article also records Hodge-line, relative Iitaka and weak-effectivity inputs from OILS, outside the 14-paper inventory.

What this map checks

OpenAI Research Catalog · 034 · p. 5 ↗
Official catalogue at the reference commit ↗
CONTENTS.md: Log abundance for compact Kähler spaces under logarithmic Iitaka subadditivity
Source snapshot: adc7f1241b42e322a6451854ab7e4b4c146bf78a

Enlarged figure

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