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We prove that the non-nef locus and the restricted base locus of a pseudoeffective divisor coincide on KLT pairs. We also extend to KLT pairs F. Russo's characterization of nef and abundant divisors by means of asymptotic multiplier ideals.

代数几何 · 数学 2012-10-19 Salvatore Cacciola , Lorenzo Di Biagio

Given a projective hyper-K\"ahler manifold $X$, we study the asymptotic base loci of big divisors on $X$. We provide a numerical characterization of these loci and study how they vary while moving a big divisor class in the big cone, using…

代数几何 · 数学 2024-06-27 Francesco Antonio Denisi , Ángel David Ríos Ortiz

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…

代数几何 · 数学 2019-02-20 Caucher Birkar , Zhengyu Hu

We show that the augmented base locus coincides with the exceptional locus (i.e. null locus) for any nef $\mathbb{R}$-Cartier divisor on any scheme projective over a field (of any characteristic). Next we prove a semi-ampleness criterion in…

代数几何 · 数学 2013-12-03 Caucher Birkar

We generalize Nakamaye's description, via intersection theory, of the augmented base locus of a big and nef divisor on a normal pair with log-canonical singularities or, more generally, on a normal variety with non-lc locus of dimension at…

代数几何 · 数学 2014-12-24 Salvatore Cacciola , Angelo Felice Lopez

We prove the termination of flips for 4-dimensional pseudo-effective NQC log canonical generalized pairs. As main ingredients, we verify the termination of flips for 3-dimensional NQC log canonical generalized pairs, and show that the…

代数几何 · 数学 2024-04-16 Guodu Chen , Nikolaos Tsakanikas

We show that minimal models of $\mathbb{Q}$-factorial NQC log canonical generalised pairs exist, assuming the existence of minimal models of smooth varieties. More generally, we prove that on a $\mathbb{Q}$-factorial NQC log canonical…

Given an NQC log canonical generalized pair $(X,B+M)$ whose underlying variety $X$ is not necessarily $\mathbb{Q}$-factorial, we show that one may run a $(K_X+B+M)$-MMP with scaling of an ample divisor which terminates, provided that…

代数几何 · 数学 2025-09-19 Nikolaos Tsakanikas , Lingyao Xie

The purpose of this paper is to define and study systematically some asymptotic invariants associated to base loci of line bundles on smooth projective varieties. We distinguish an open dense subset of the real big cone, called the stable…

代数几何 · 数学 2007-05-23 Lawrence Ein , Robert Lazarsfeld , Mircea Mustata , Michael Nakamaye , Mihnea Popa

Let $(X, \Delta)$ be a projective log canonical Calabi-Yau pair and $L$ an ample $\mathbb{Q}$-line bundle on $X$, we show that there is a correspondence between lc places of $(X, \Delta)$ and weakly special test configurations of $(X,…

代数几何 · 数学 2025-01-07 Guodu Chen , Chuyu Zhou

In this paper, we study the relative anti-canonical divisor $-K_{X/Y}$ of an algebraic fiber space $\phi: X \to Y$, and we reveal relations among positivity conditions of $-K_{X/Y}$, certain flatness of direct image sheaves, and variants of…

代数几何 · 数学 2020-05-12 Sho Ejiri , Masataka Iwai , Shin-ichi Matsumura

We establish a Koll\'ar-type gluing theory for NQC generalized log canonical pairs and use it to prove semi-ampleness results of NQC generalized pairs. As consequences, we prove the existence of flips for any NQC generalized log canonical…

代数几何 · 数学 2023-06-05 Jihao Liu , Lingyao Xie

In this paper, we give a characterization of Fano type varieties in terms of the asymptotic base loci of $-(K_X+\Delta)$. We also show that for a potentially lc pair $(X,\Delta)$, if no plc centers are contained in the augmented base locus…

代数几何 · 数学 2025-06-17 Sung Rak Choi , Sungwook Jang , Dae-Won Lee

We show that if a divisor centered over a point on a smooth surface computes a minimal log discrepancy, then the divisor also computes a log canonical threshold. To prove the result, we study the asymptotic log canonical threshold of the…

代数几何 · 数学 2017-06-08 Harold Blum

Let $(X/Z,B+A)$ be a $\Q$-factorial dlt pair where $B,A\ge 0$ are $\Q$-divisors and $K_X+B+A\sim_\Q 0/Z$. We prove that any LMMP$/Z$ on $K_X+B$ with scaling of an ample$/Z$ divisor terminates with a good log minimal model or a Mori fibre…

代数几何 · 数学 2012-04-25 Caucher Birkar

The nonvanishing conjecture for projective log canonical pairs plays a key role in the minimal model program of higher dimensional algebraic geometry. The numerical nonvanishing conjecture considered in this paper is a weaker version of the…

代数几何 · 数学 2020-02-05 Jingjun Han , Wenfei Liu

We prove a base point free theorem for nef and log big divisors on log canonical surfaces.

alg-geom · 数学 2008-02-03 Shigetaka Fukuda

The LCS locus is an essential ingredient in the proof of fundamental results of Log Minimal Model Program, such as nonvanishing and base point freeness theorems. We prove in this paper that the LCS locus of a log canonical variety has…

代数几何 · 数学 2007-05-23 Florin Ambro

We prove the Nonvanishing conjecture for uniruled projective log canonical pairs of dimension $n$, assuming the Nonvanishing conjecture for smooth projective varieties in dimension $n-1$. We also show that the existence of good minimal…

代数几何 · 数学 2022-05-23 Vladimir Lazić , Fanjun Meng

We approach non-divisorial base loci of big and nef line bundles on irreducible symplectic varieties. While for K3 surfaces, only divisorial base loci can occur, nothing was known about the behaviour of non-divisorial base loci for more…

代数几何 · 数学 2019-01-24 Ulrike Riess
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