Family 034Algebraic and complex geometryNo LeanNot yet digested
Log abundance for compact Kähler spaces under logarithmic Iitaka subadditivity
Using logarithmic Iitaka subadditivity, proves log abundance in every dimension for normal compact Kähler log canonical pairs with effective rational boundary: an analytically nef ℚ-Cartier adjoint is semiample. It also proves projective log abundance over every algebraically closed field of characteristic zero and the effective Iitaka fibration conjecture for smooth projective varieties of nonnegative Kodaira dimension in that setting. A further result resolves the finite-rational-coefficient index conjecture for connected projective semi-log-canonical log Calabi–Yau pairs over such fields in each fixed dimension and for each fixed finite set of rational boundary coefficients, with a uniform index independent of the number of components.
Manuscripts in this family · 14
Log abundance for compact Kähler spaces under logarithmic Iitaka subadditivity
Oct 6, 2026·main.pdf
Assume logarithmic Iitaka subadditivity for surjective morphisms with connected fibers between smooth projective complex varieties with compatible reduced simple normal crossing boundaries. We prove log abundance for normal irreducible compact Kähler spaces in every dimension: for a log canonical pair with effective rational boundary and ℚ-Cartier, analytic nefness of implies semiampleness.
Uniform indices for semi-log-canonical log Calabi–Yau pairs
Oct 5, 2026·uniform-slc-index.pdf
We prove a uniform index theorem for connected projective semi-log-canonical log Calabi–Yau pairs in every fixed dimension at least four over an algebraically closed field of characteristic zero. For boundary coefficients in a fixed finite rational set, a single multiple of the log canonical divisor is Cartier and linearly trivial. The multiple depends only on the dimension and coefficient set, not on the number of irreducible components. Together with the established theorem in dimensions at most three, this resolves the finite-rational-coefficient semi-log-canonical index conjecture.
Conditional good minimal models for compact Kähler fourfolds
Oct 6, 2026·paper.pdf
Assuming orbifold Iitaka subadditivity and abundance for nef fourfold adjoints of nonnegative Kodaira dimension, we prove the existence of good minimal models for globally strongly ℚ-factorial compact Kähler klt fourfold pairs with effective rational boundary and analytically pseudo-effective actual ℚ-Cartier adjoint. The ordinary fourfold minimal model program supplies the nef endpoint. We prove nonvanishing by fibration arguments and, in algebraic dimension zero, by singular metrics, holomorphic foliations, and extension from a reduced boundary. The projective abundance argument used in the proof is included in full.
Log abundance in characteristic zero
Sep 24, 2026·paper.pdf
We prove the rational-boundary log abundance conjecture in every dimension over algebraically closed fields of characteristic zero: every nef ℚ-Cartier log canonical divisor on a projective log canonical pair with effective rational boundary is semiample. Over ℂ, the proof also establishes canonical nonvanishing for smooth projective varieties in every dimension.
Minimal metrics and interior injectivity for nef adjoints
Sep 27, 2026·paper.pdf
Let be a projective complex klt pair with effective rational boundary and nef ℚ-Cartier adjoint. On any projective log resolution, minimal semipositive metrics on the pulled-back adjoint exist and have zero Lelong numbers everywhere. On smooth projective complex varieties, we also prove an H-injectivity theorem for rational interior boundaries with simple-normal-crossing support when both endpoint bundles carry zero-Lelong semipositive metrics.
Fourfold nonvanishing by minimal metrics and moving jets
Sep 27, 2026·paper.pdf
We prove canonical nonvanishing for smooth connected projective complex fourfolds: if K is pseudo-effective, then for some positive integer m.
Lifting sections from the reduced support of an adjoint
Sep 27, 2026·paper.pdf
For a projective ℚ-factorial dlt pair with effective rational boundary over an algebraically closed field of characteristic zero, we prove that the adjoint has positive Iitaka dimension whenever a nonzero effective Cartier multiple is supported on the coefficient-one boundary and restricts to a semiample line bundle on its whole reduced support. This gives log abundance after nonvanishing in dimension at most four over ℂ.
Schnell fiber spaces and good canonical models
Sep 24, 2026·paper.pdf
We prove the Campana–Peternell inequality for a smooth connected projective complex variety X and an effective Cartier divisor D whenever is pseudo-effective for some positive integer m. For an algebraic fiber space between smooth connected projective complex varieties, the hypothesis that is pseudo-effective with H ample Cartier gives for a very general smooth fiber F, as well as nonzero sections of for all sufficiently large divisible m.
Uniform log Iitaka fibrations and bounded moduli denominators
Oct 4, 2026·uniform-log-iitaka.pdf
For normal projective log canonical pairs over algebraically closed fields of characteristic zero, of fixed dimension d ≥ 5 and with effective boundary coefficients in a fixed finite rational set, we prove that one complete rounded pluricanonical system generates the full Iitaka field whenever the ℚ-Cartier log canonical divisor has nonnegative Kodaira dimension. Its degree depends only on the dimension and coefficient set. For the paper's normalized canonical bundle formulae over ℂ, we also bound the Cartier denominators of the moduli divisors on smooth projective determining models in terms of the dimension and coefficient set.
Uniform Pluricanonical Iitaka Fibrations
Oct 3, 2026·paper.pdf
We prove the effective Iitaka fibration conjecture in characteristic zero. For each dimension, one pluricanonical degree defines the Iitaka fibration of every smooth integral projective variety of that dimension and nonnegative Kodaira dimension over an algebraically closed field. The associated sections generate the full Iitaka function field.
Relative denominators and effective systems for log Calabi-Yau fibrations
Sep 27, 2026·paper.pdf
We prove uniform denominator and effective-system bounds for log Calabi-Yau fibrations from projective log canonical complex pairs of dimension at most four onto positive-dimensional bases, with boundary coefficients in a fixed finite rational set. The bounds give a uniform trivializing degree and a uniform b-Cartier multiple of the moduli b-divisor. When the base divisor is big, a uniform complete rounded adjoint system has section ratios generating the full base function field.
Arithmetic Stein-degree bounds for log Calabi–Yau pairs
Sep 25, 2026·paper.pdf
Fix d ≥ 1 and t > 0. Let be an ordinary projective log canonical ℚ-pair of dimension d over a characteristic-zero field k, with X normal and integral, , B effective, and . We prove that every prime component S of B with coefficient at least t satisfies , where k is the relative algebraic closure of k in . This also bounds the Stein degree of S over k, proving the contraction-to-a-point formulation of Birkar's Stein-degree conjecture for ordinary ℚ-pairs.
Uniform effective log Iitaka fibrations for fourfolds
Sep 26, 2026·paper.pdf
We prove the finite-rational-coefficient case of the effective log Iitaka conjecture in dimension four. For normal projective log canonical complex fourfolds with boundary coefficients in a fixed finite rational set and pseudo-effective rational Cartier adjoint, one uniform degree makes the complete rounded reflexive system nonempty and its section ratios generate the full Iitaka field. We also prove a uniform canonical index bound for projective klt complex fourfolds with rationally trivial canonical divisor.
Abundance after nonvanishing for compact Kähler fourfolds
Sep 27, 2026·paper.pdf
We prove semiampleness of the actual ℚ-Cartier adjoint of a normal connected compact Kähler klt fourfold whenever it is analytically nef and some positive Cartier multiple has a nonzero section. The boundary is effective and rational; the fourfold need not be projective or ℚ-factorial. In Iitaka dimension zero, a positive Cartier multiple is the trivial holomorphic line bundle.