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We sketch a proof of the abundance conjecture that the Kodaira dimension of a compact complex algebraic manifold equals its numerical Kodaira dimension. The proof consists of the following three parts: (i) the case of numerical Kodaira…

Algebraic Geometry · Mathematics 2010-06-29 Yum-Tong Siu

We give another alternative proof to the Kawamata semiampleness theorem for the log canonical divisors on klt varieties which are nef and abundant. After the first version of this article was posted to the e-print Arxiv, Prof. Fujino…

Algebraic Geometry · Mathematics 2019-03-22 Shigetaka Fukuda

We prove the existence of a Mori contraction on a compact Kaehler threefold whose canonical bundle is (analytically) not nef if the threefold can be approximated by projective threefolds or if the algebraic dimension is 2.

Algebraic Geometry · Mathematics 2007-05-23 Thomas Peternell

Let X be a compact K\"ahler threefold that is not uniruled. We prove that X has a minimal model.

Algebraic Geometry · Mathematics 2017-11-27 Andreas Höring , Thomas Peternell

The paper is part of an attempt of understanding non-K\"ahler threefolds. We start by looking at compact complex non-K\"ahler threefolds with algebraic dimension two and admitting locally conformally K\"ahler metrics. Under certain…

Differential Geometry · Mathematics 2023-03-21 Daniele Angella , Maurizio Parton , Victor Vuletescu

Let $X$ be a compact K\"ahler manifold and let $(L, \varphi)$ be a pseudo-effective line bundle on $X$. We first define a notion of numerical dimension of pseudo-effective line bundles with singular metrics, and then discuss the properties…

Algebraic Geometry · Mathematics 2019-02-20 Junyan Cao

Let $f : (X, \Delta) \to Y$ be a flat, projective family of sharply $F$-pure, log-canonically polarized pairs over an algebraically closed field of characteristic $p >0$ such that $p \nmid \ind(K_{X/Y} + \Delta)$. We show that $K_{X/Y} +…

Algebraic Geometry · Mathematics 2015-04-28 Zsolt Patakfalvi

Semi-log canonical varieties are a higher-dimensional analogue of stable curves. They are the varieties appearing as the boundary $\Delta$ of a log canonical pair $(X,\Delta)$, and also appear as limits of canonically polarized varieties in…

Algebraic Geometry · Mathematics 2019-08-14 Morgan V Brown

We prove that if $(X,\Delta)$ is a threefold pair with mild singularities such that ${-}(K_X+\Delta)$ is nef, then the numerical class of ${-}(K_X+\Delta)$ is effective.

Algebraic Geometry · Mathematics 2023-12-14 Vladimir Lazić , Shin-ichi Matsumura , Thomas Peternell , Nikolaos Tsakanikas , Zhixin Xie

Let $(X,g)$ be a compact Riemannian manifold with quasi-positive Riemannian scalar curvature. If there exists a complex structure $J$ compatible with $g$, then the canonical bundle $K_X$ is not pseudo-effective and the Kodaira dimension…

Differential Geometry · Mathematics 2017-06-06 Xiaokui Yang

In this short note, we consider the conjecture that the log canonical divisor (resp. the anti-log canonical divisor) $K_X + \Delta$ (resp. $-(K_X + \Delta)$) on a pair $(X, \Delta)$ consisting of a complex projective manifold $X$ and a…

Algebraic Geometry · Mathematics 2007-05-23 Shigetaka Fukuda

In this paper we consider left-invariant pseudo-K\"{a}hler structures on six-dimensional nilpotent Lie algebras. The explicit expressions of the canonical complex structures are calculated, and the curvature properties of the associated…

Differential Geometry · Mathematics 2013-11-15 N. K. Smolentsev

We conjecture the equality of the numerical and Kodaira dimensions $\nu_1^*(X)$ and $\kappa_1^*(X)$ for the cotangent bundle of compact K\"ahler manifolds $X$, generalising the classical case of the canonical bundle. We show or reduce it to…

Algebraic Geometry · Mathematics 2023-03-07 Frederic Bruno Campana

We provide families of compact $(n + 1)$-dimensional complex non K\"ahler manifolds satisfying the $\partial\bar{\partial}$-Lemma, with holomoprhically trivial canonical bundle, carrying a balanced metric and with no $p$-K\"ahler…

Differential Geometry · Mathematics 2024-03-18 Andrea Cattaneo , Adriano Tomassini

We classify non-algebraic compact K\"ahler threefolds admitting an endomorphism $f: X \to X$ of degree at least two.

Algebraic Geometry · Mathematics 2017-11-10 Andreas Höring , Thomas Peternell

We study the complex-analytic geometry of semi-positive holomorphic line bundles on compact K\"ahler manifolds. In one of our main results, for a $\mathbb{Q}$-effective line bundle satisfying a natural torsion-type assumption, we show the…

Complex Variables · Mathematics 2026-01-23 Takayuki Koike

In this short note, we prove the existence of constant scalar curvature K\"ahler metrics on compact K\"ahler manifolds with semi-ample canonical bundles.

Differential Geometry · Mathematics 2018-05-18 Wangjian Jian , Yalong Shi , Jian Song

A conformal transformation of a semi-Riemannian manifold is essential if there is no conformally equivalent metric for which it is an isometry. For Riemannian manifolds the existence of an essential conformal transformation forces the…

Differential Geometry · Mathematics 2024-09-24 Vicente Cortés , Thomas Leistner

In continuation of our paper in Math. Ann. 333 we classify smooth complex projective threefolds X with -K_X big and nef but not ample and Picard number 2, whose anticanonical map is small. We assume also that the Mori contraction of X and…

Algebraic Geometry · Mathematics 2007-10-16 Priska Jahnke , Thomas Peternell , Ivo Radloff

We study the stability of compact pseudo-K\"ahler manifolds, i.e. compact complex manifolds $X$ endowed with a symplectic form compatible with the complex structure of $X$. When the corresponding metric is positive-definite, $X$ is K\"ahler…

Differential Geometry · Mathematics 2020-01-15 Adela Latorre , Luis Ugarte