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14294357 · Apr 202619922001200920172026
48 results for nef anti-canonical bundle

Study Miyaoka-Yau inequality for certain projective manifolds.

problem Proving Miyaoka-Yau inequality for specific types of manifolds.
method Using recent work by K.~Zhang and delta-invariant introduced by Fujita and Odaka.
result Established Miyaoka-Yau type inequality for projective manifolds with nef anti-canonical line bundle.

Paper proves structure of compact Kähler 3-folds with specific bundles.

problem Characterizing compact Kähler 3-folds with nef anti-canonical bundles.
method Minimal Model Program, positivity of direct image sheaves, Q-conic bundles, orbifold vector bundles.
result Compact Kähler 3-folds with nef anti-canonical bundles are essentially one of three types.

The paper shows how compact Kähler manifolds with a special bundle can be broken down into simpler parts.

problem Understanding compact Kähler manifolds with a specific type of anti-canonical bundle.
method Introduced a new approach to extend a strategy from smooth projective varieties to singular Kähler spaces, using a flatness criterion for pseudo-effective sheaves.
result Compact Kähler manifolds with a nef anti-canonical bundle admit a locally trivial fibration with rational connected fibers and a Calabi-Yau base.

The paper studies fundamental groups of compact Kahler varieties with nef anti-canonical bundles.

problem Understanding the fundamental groups of compact Kahler varieties with specific properties.
method Application of geometric analytic theory of Kahler spaces and study of Albanese maps.
result The fundamental group of compact Kahler varieties with nef anti-canonical bundle is almost Abelian.

The paper studies foliations on smooth projective varieties and their properties.

problem Characterizing and understanding foliations on smooth projective varieties.
method Develops a structure theorem for smooth projective varieties with almost nef regular foliations, using a smooth morphism and MRC fibration.
result An almost nef regular foliation on a smooth projective variety can be decomposed into a numerically flat regular foliation and a smooth morphism.

Study projective klt pairs with nef anti-canonical divisor and their properties.

problem Characterize properties of projective klt pairs with nef anti-log canonical divisors.
method Analyze maximally rationally connected fibration and use numerical dimension analogy.
result Numerical dimension of anti-log canonical divisor on XX matches that on a general fiber.

The paper proves inequalities for orbifold second Chern classes in Fujiki's class.

problem Inequalities for orbifold second Chern classes of compact normal analytic varieties.
method Generic nefness theorems for tangent and cotangent sheaves, and an orbifold Bogomolov--Gieseker inequality for mixed polarizations.
result Semipositivity of the orbifold second Chern class for varieties with nef anti-canonical divisor.

Study positive characteristic Fano 4-folds with nef tangent bundles.

problem Positive characteristic version of the Campana-Peternell conjecture for Fano 4-folds.
method Analyzes Fano 4-folds with nef tangent bundles in positive characteristic.
result Affirmative answer for Fano 4-folds with Picard number > 1 and nef tangent bundle.

The paper classifies certain singular projective varieties with specific properties.

problem Classifying projective klt pairs with nef anti-log canonical divisors.
method Establishes a structure theorem using locally trivial rationally connected fibrations.
result Projective klt pairs can be decomposed into rationally connected and Calabi-Yau varieties.

In this paper, we show that if the tangent bundle of a smooth projective variety is strictly nef, then it is isomorphic to a projective space; if a projective variety XnX^n (n>4)(n>4) has strictly nef Λ2TXΛ^2 TX, then it is isomorphic to Pn\mathbb{P}^n or quadric Qn\mathbb{Q}^n. We also prove that on elliptic curves, strict…

2016-09-22abs ↗pdf ↗

The paper proves structures for complex projective varieties with certain tangent bundle properties.

problem Characterizing complex projective varieties based on properties of their tangent bundles.
method Analyzing the positivity of exterior powers of tangent bundles and using étale covers.
result Complex projective varieties with nef exterior powers of tangent bundles are Fano fiber spaces over Abelian varieties.

Projective manifolds with specific bundles are isomorphic to simpler spaces.

problem Characterizing projective manifolds with tangent bundles containing strictly nef subsheaves.
method Analyzing the structure of the tangent bundle and using properties of strictly nef subsheaves.
result Projective manifolds with the described bundles are isomorphic to projective bundles over hyperbolic manifolds or projective spaces.

Fundamental groups of certain Kähler orbifolds have polynomial growth.

problem Understanding the fundamental groups of specific types of orbifolds.
method Analyzing the orbifold fundamental group with respect to the nef anticanonical bundle.
result The orbifold fundamental group has polynomial growth.

Holomorphic vector fields and anti-canonical divisors on complex manifolds are studied.

problem Existence of non-trivial holomorphic vector fields on compact complex manifolds.
method Vanishing result for measure preserving holomorphic vector fields, Gibbs stability, and log terminal singularities.
result No non-trivial holomorphic vector fields on compact complex manifolds with big anti-canonical line bundle.

Study the Albanese map for Kähler manifolds with nef anticanonical bundle.

problem Characterize the structure of the Albanese map for Kähler manifolds with nef anticanonical bundle.
method Analyze two cases: general fiber is Calabi-Yau or projective space. Provide proofs for both cases.
result For the case where the general fiber is Calabi-Yau, the manifold itself must be Calabi-Yau.

In this paper, we study smooth complex projective varieties XX such that some exterior power rTX\bigwedge^r T_X of the tangent bundle is strictly nef. We prove that such varieties are rationally connected. We also classify the following two cases. If TXT_X is strictly nef, then XX isomorphic to the projective space $\…

2018-01-28abs ↗pdf ↗

The paper proves conditions for minimal compact Kähler manifolds with vanishing second Chern class.

problem Conditions for minimal compact Kähler manifolds with vanishing second Chern class.
method Study of the abundance conjecture and associated Iitaka fibrations.
result For a minimal compact Kähler manifold, the second Chern class vanishes if and only if the cotangent bundle is nef and the canonical bundle has numerical dimension 0 or 1.

The paper establishes inequalities for Chern classes and numbers on polarized manifolds and nef vector bundles.

problem Chern class and number inequalities on polarized manifolds and nef vector bundles.
method Sharp inequalities derived from polarized pairs and nef vector bundles.
result Bounding Chern numbers of nef vector bundles and classifying compact Kähler manifolds.

Study of tangent bundle positivity on complex projective varieties.

problem Positivity of the second exterior power of tangent bundles on smooth complex projective varieties.
method Analyzes properties of tangent bundles and uses algebraic geometry techniques.
result Proves that up to a finite cover, the Albanese map is a locally trivial fibration with nef fibers.

Counterexample disproves log canonical Beauville--Bogomolov decomposition.

problem Disproving the log canonical Beauville--Bogomolov decomposition.
method Constructing a specific log canonical, K-trivial variety with non-birational fibers.
result Provides a counterexample to the Beauville--Bogomolov decomposition in the log canonical setting.

Two types of nonvanishing results are presented for compact Kähler varieties.

problem Deriving geometric consequences from numerical information in Kähler geometry.
method Analyzing non-uniruled varieties and hyperkähler manifolds to establish nonvanishing results for adjoint and nef bundles.
result Strong abundance-type results are obtained in dimension 4.

The paper classifies minimal projective varieties satisfying a specific equality.

problem Classifying minimal projective varieties with a specific equality.
method Established a structure theorem for minimal projective klt varieties satisfying Miyaoka's equality.
result Minimal projective klt varieties with Miyaoka's equality have semi-ample canonical divisors and specific Kodaira dimensions.

Introduce generalized Ueda obstruction classes for line bundles and apply them to non-semi-positivity.

problem Non-semi-positivity of line bundles
method Introduce generalized Ueda obstruction classes and use Dolbeault resolution
result Recover classical examples and provide new examples of nef but not semi-positive line bundles

Estimates Lelong numbers of Monge-Ampère products for Kähler manifolds.

problem Estimating Lelong numbers of Monge-Ampère products on Kähler manifolds.
method Analyzes generalized Monge-Ampère products and applies estimates to Chern and Segre currents of pseudoeffective vector bundles.
result Generalizes a recent result about pseudoeffective vector bundles and their nefness.

Criterion for projectivisation on klt spaces, characterizing quotients and stability.

problem Characterizing finite quotients of projective spaces and Abelian varieties.
method Criterion based on reflexive sheaves and stability conditions.
result Characterization of finite quotients using Q\mathbb{Q}-Chern class inequalities and stability condition.

Paper proves Hermitian-Yang-Mills metrics for stable Kähler bundles.

problem Existence of Hermitian-Yang-Mills metrics for Kähler vector bundles.
method Analyzes slope polystability and uses Kähler currents with singularities.
result Validates existence of Hermitian-Yang-Mills metrics for stable bundles and nef-big currents.

The study of projective varieties with nef anticanonical divisors and log terminal singularities.

problem Understanding the structure and properties of projective varieties with specific divisor conditions.
method Analyzing the Albanese map and MRC fibration for klt projective varieties, showing locally constant fibrations and product decompositions.
result Generalization of results for smooth projective varieties to the klt case, including decomposition into rationally connected and projective varieties with trivial canonical divisor.

Let MM and NN be two compact complex manifolds. We show that if the tautological line bundle OTM(1)\mathscr{O}_{T_M^*}(1) is not pseudo-effective and OTN(1)\mathscr{O}_{T_N^*}(1) is nef, then there is no non-constant holomorphic map from MM to NN. In particular, we prove that any holomorphic map from a compact complex mani…

2018-07-07abs ↗pdf ↗

Let (X,D)(X, D) be a logarithmic pair, and let hh be a singular metric on the tangent bundle, smooth on the open part of XX. We give sufficient conditions on the curvature of hh for the logarithmic and the standard cotangent bundles to be big. As an application, we give a metric proof of the bigness of logarithmic cota…

2016-06-17abs ↗pdf ↗

For a generic anti-canonical hypersurface in each smooth toric Fano 4-fold with rank 2 Picard group, we prove there exist three isolated rational curves in it. Moreover, for all these 4-folds except one, the contractions of generic anti-canonical hypersurfaces along the three rational curves can be deformed to smooth t…

2010-12-01abs ↗pdf ↗

We show that a compact Kahler manifold with nonpositive holomorphic sectional curvature has nef canonical bundle. If the holomorphic sectional curvature is negative then it follows that the canonical bundle is ample, confirming a conjecture of Yau. The key ingredient is the recent solution of this conjecture in the pro…

2015-06-03abs ↗pdf ↗

Let XX be a smooth variety and let LL be an ample line bundle on XX. If π1alg(X)π^{alg}_{1}(X) is large, we show that the Seshadri constant ε(pL)ε(p^{*}L) can be made arbitrarily large by passing to a finite étale cover p:XXp:X'\rightarrow X. This result answers affirmatively a conjecture of J.-M. Hwang. Moreover, we prove an …

2014-11-04abs ↗pdf ↗