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Given a path of almost-K\"ahler metrics compatible with a fixed symplectic form on a compact 4-manifold such that at time zero the almost-K\"ahler metric is an extremal K\"ahler one, we prove, for a short time and under a certain…

Differential Geometry · Mathematics 2010-04-22 Mehdi Lejmi

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

In this article we study compact K\"ahler manifolds $X$ admitting non-singular holomorphic vector fields with the aim of extending to this setting the classical birational classification of projective varieties with tangent vector fields.…

Algebraic Geometry · Mathematics 2010-07-20 Jaume Amoros , Monica Manjarin , Marcel Nicolau

Let $\mathbb{K}$ be an algebraically closed field of characteristic $p>5$. We show the existence of minimal models for pseudo-effective NQC lc generalized pairs in dimension three over $\mathbb{K}$. As a consequence, we prove the…

Algebraic Geometry · Mathematics 2024-11-21 Tianle Yang , Zelin Ye , Zhiyao Zhang

Let $(X,B)$ be a projective log canonical pair such that $B$ is a $\Q$-divisor, and that there is a surjective morphism $f\colon X\to Z$ onto a normal variety $Z$ satisfying: $K_X+B\sim_\Q f^*M$ for some $\Q$-divisor $M$, and the augmented…

Algebraic Geometry · Mathematics 2019-02-20 Caucher Birkar , Zhengyu Hu

In this article we show that if $(X, \Delta)$ is a log canonical compact K\"ahler $3$-fold such that $K_X+\Delta$ is nef and the numerical dimension $\nu(K_X+\Delta)\neq 2$, then $K_X+\Delta$ is semi-ample.

Algebraic Geometry · Mathematics 2023-02-22 Omprokash Das , Wenhao Ou

We consider the minimal model program for varieties that are not Q-factorial. We show that, in many cases, its steps are simpler than expected. In particular, all flips are 1-complemented. The main applications are to log terminal…

Algebraic Geometry · Mathematics 2021-02-02 János Kollár

Minimal model conjecture for a proper variety $X$ is that if $\kappa(X)\geq 0$, then $X$ has a minimal model with the abundance and if $\kappa =-\infty$, then $X$ is birationally equivalent to a variety $Y$ which has a fibration $Y \to Z$…

alg-geom · Mathematics 2008-02-03 Shihoko Ishii

Let $(X,\Delta)$ be a log canonical pair over $\mathbb{C}$ with $X$ a normal projective variety, $\Delta$ an effective $\mathbb{Q}$-divisor, and $K_X+\Delta$ nef. We give a non-vanishing criterion for $K_X+\Delta$ in dimension $n$ with $X$…

Algebraic Geometry · Mathematics 2019-08-02 Fanjun Meng

In this paper, we prove the cone theorem and the contraction theorem for pairs $(X, B)$, where $X$ is a normal variety and $B$ is an effective $\mathbb R$-divisor on $X$ such that $K_X+B$ is $\mathbb R$-Cartier.

Algebraic Geometry · Mathematics 2010-08-17 Osamu Fujino

In this article we show that if $(X, \Delta)$ is a log canonical compact K\"ahler threefold pair such that $K_X+\Delta$ is nef and the numerical dimension $\nu(X, K_X+\Delta)=2$, then $K_X+\Delta$ is semi-ample. This result combined with…

Algebraic Geometry · Mathematics 2025-06-13 Omprokash Das , Wenhao Ou

Minimal log discrepancies (mld's) are related not only to termination of log flips, and thus to the existence of log flips but also to the ascending chain condition (acc) of some global invariants and invariants of singularities in the Log…

Algebraic Geometry · Mathematics 2007-05-23 Caucher Birkar , V. V. Shokurov

For $\mathbb Q$-factorial klt algebraically integrable adjoint foliated structures, we prove the cone theorem, the contraction theorem, and the existence of flips. Therefore, we deduce the existence of the minimal model program for such…

Algebraic Geometry · Mathematics 2024-08-27 Paolo Cascini , Jingjun Han , Jihao Liu , Fanjun Meng , Calum Spicer , Roberto Svaldi , Lingyao Xie

To construct a resulting model in LMMP is sufficient to prove existence of log flips and their termination for certain sequences. We prove that LMMP in dimension $d-1$ and termination of terminal log flips in dimension $d$ imply, for any…

Algebraic Geometry · Mathematics 2007-05-23 V. V. Shokurov

It is proved by M. Paun (1997, 2017) that the fundamental group of a compact Kahler manifold X is almost Abelian if the anti-canonical bundle -KX is nef. In this paper, we apply the recent geometric analytic theory of Kahler spaces…

Algebraic Geometry · Mathematics 2026-02-10 Xin Fu , Bin Guo , Jian Song , Juanyong Wang

The Hassett--Keel program seeks to give a modular interpretation to the steps of the log minimal model program of $\overline{\mathcal{M}}_g$. The goal of this paper is to complete the Hassett--Keel program in genus four, supplementing…

Algebraic Geometry · Mathematics 2025-04-30 Kenneth Ascher , Kristin DeVleming , Yuchen Liu , Xiaowei Wang

Let $(X,\Delta)$ be a smooth complex projective simple normal crossing pair of dimension $n\geq 3$ endowed with an everywhere nondegenerate logarithmic conformal tensor. If $K_X+\Delta$ is not nef, then precisely one of the following…

Algebraic Geometry · Mathematics 2026-04-20 Maurício Corrêa , Alex Massarenti

We show the existence of strictly almost-Kahler anti-self-dual metrics on certain 4-manifolds by deforming scalar-flat Kahler metrics. On the other hand, we prove the non-existence of such metrics on certain other 4-manifolds by means of…

Differential Geometry · Mathematics 2015-11-25 Inyoung Kim

We prove the existence of flips for $\mathbb Q$-factorial NQC generalized lc pairs, and the cone and contraction theorems for NQC generalized lc pairs. This answers a question of C. Birkar which was conjectured by J. Han and Z. Li. As an…

Algebraic Geometry · Mathematics 2021-09-10 Christopher D. Hacon , Jihao Liu

The Minimal Model Program offers natural higher-dimensional analogues of stable $n$-pointed curves and maps: stable pairs consisting of a projective variety $X$ of dimension $\ge2$ and a divisor $B$, that should satisfy a few simple…

Algebraic Geometry · Mathematics 2007-05-23 Valery Alexeev