scholarly journals Log pluricanonical representations and the abundance conjecture

2014 ◽  
Vol 150 (4) ◽  
pp. 593-620 ◽  
Author(s):  
Osamu Fujino ◽  
Yoshinori Gongyo
Keyword(s):  
Canonical Divisor ◽  
Log Canonical ◽  
Canonical Pair

AbstractWe prove the finiteness of log pluricanonical representations for projective log canonical pairs with semi-ample log canonical divisor. As a corollary, we obtain that the log canonical divisor of a projective semi log canonical pair is semi-ample if and only if the log canonical divisor of its normalization is semi-ample. We also treat many other applications.

scholarly journals Polarized pairs, log minimal models, and Zariski decompositions

2014 ◽  
Vol 215 ◽  
pp. 203-224 ◽  
Author(s):  
Caucher Birkar ◽  
Zhengyu Hu
Keyword(s):  
Minimal Model ◽  
Birational Geometry ◽  
Minimal Models ◽  
Positive Part ◽  
Log Canonical ◽  
Canonical Pair ◽  
The Way

AbstractWe continue our study of the relation between log minimal models and various types of Zariski decompositions. Let (X,B) be a projective log canonical pair. We will show that (X,B) has a log minimal model if either KX + B birationally has a Nakayama–Zariski decomposition with nef positive part, or if KX +B is big and birationally has a Fujita–Zariski or Cutkosky–Kawamata–Moriwaki–Zariski decomposition. Along the way we introduce polarized pairs (X,B +P), where (X,B) is a usual projective pair and where P is nef, and we study the birational geometry of such pairs.

Semi-Normal Log Centres and Deformations of Pairs

2013 ◽  
Vol 57 (1) ◽  
pp. 191-199 ◽  
Author(s):  
János Kollár
Keyword(s):  
Log Canonical ◽  
Canonical Pair

AbstractWe show that some of the properties of log canonical centres of a log canonical pair also hold for certain subvarieties that are close to being a log canonical centre. As a consequence, we obtain that, in working with deformations of pairs where all the coefficients of the boundary divisor are bigger than ½, embedded points never appear on the boundary divisor.

scholarly journals Polarized pairs, log minimal models, and Zariski decompositions

2014 ◽  
Vol 215 ◽  
pp. 203-224
Author(s):  
Caucher Birkar ◽  
Zhengyu Hu
Keyword(s):  
Minimal Model ◽  
Birational Geometry ◽  
Minimal Models ◽  
Positive Part ◽  
Log Canonical ◽  
Canonical Pair ◽  
The Way

AbstractWe continue our study of the relation between log minimal models and various types of Zariski decompositions. Let (X,B) be a projective log canonical pair. We will show that (X,B) has a log minimal model if eitherKX+Bbirationally has a Nakayama–Zariski decomposition with nef positive part, or ifKX+Bis big and birationally has a Fujita–Zariski or Cutkosky–Kawamata–Moriwaki–Zariski decomposition. Along the way we introduce polarized pairs (X,B+P), where (X,B) is a usual projective pair and wherePis nef, and we study the birational geometry of such pairs.

scholarly journals Log canonical pairs with good augmented base loci

2014 ◽  
Vol 150 (4) ◽  
pp. 579-592 ◽  
Author(s):  
Caucher Birkar ◽  
Zhengyu Hu
Keyword(s):  
Minimal Model ◽  
Surjective Morphism ◽  
Normal Variety ◽  
Base Locus ◽  
Log Canonical ◽  
Canonical Pair ◽  
Interesting Special Case ◽  
Base Loci ◽  
Special Case

AbstractLet $(X,B)$ be a projective log canonical pair such that $B$ is a $\mathbb{Q}$-divisor, and that there is a surjective morphism $f: X\to Z$ onto a normal variety $Z$ satisfying $K_X+B\sim _{\mathbb{Q}} f^*M$ for some big $\mathbb{Q}$-divisor $M$, and the augmented base locus ${\mathbf{B}}_+(M)$ does not contain the image of any log canonical centre of $(X,B)$. We will show that $(X,B)$ has a good log minimal model. An interesting special case is when $f$ is the identity morphism.

scholarly journals On numerically effective log canonical divisors

2002 ◽  
Vol 30 (9) ◽  
pp. 521-531 ◽  
Author(s):  
Shigetaka Fukuda
Keyword(s):  
Complex Numbers ◽  
Canonical Divisor ◽  
Log Canonical ◽  
Iitaka Dimension

Let(X,Δ)be a4-dimensional log variety which is proper over the field of complex numbers and with only divisorial log terminal singularities. The log canonical divisorKX+Δis semiample, if it is numerically effective (NEF) and the Iitaka dimensionκ(X,KX+Δ)is strictly positive. For the proof, we use Fujino's abundance theorem for semi-log canonical threefolds.

scholarly journals The Dual Complex of a Semi-log Canonical Surface

2021 ◽  
Author(s):  
Morgan V Brown
Keyword(s):  
Minimal Model ◽  
Stable Curves ◽  
Log Canonical ◽  
Canonical Pair ◽  
Higher Dimensional ◽  
Canonical Surface ◽  
Dual Complex ◽  
Moduli Theory

Abstract 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 moduli theory. For certain three-fold pairs $(X,\Delta ),$ we show how to compute the PL homeomorphism type of the dual complex of a dlt minimal model directly from the normalization data of $\Delta $.

scholarly journals On the semiampleness of the positive part of CKM Zariski decompositions

2013 ◽  
Vol 156 (1) ◽  
pp. 1-23 ◽  
Author(s):  
SALVATORE CACCIOLA
Keyword(s):  
Graded Rings ◽  
Positive Part ◽  
Finite Generation ◽  
Canonical Divisor ◽  
Log Canonical

AbstractWe study graded rings associated to big divisors on LC pairs whose difference with the log-canonical divisor is nef. For divisors that are positive enough at the LC centers of the pair, we prove the finite generation of such rings if the pair is DLT or the dimension is low, given that a Zariski decomposition exists.

scholarly journals Semiample perturbations for log canonical varieties over an F-finite field containing an infinite perfect field

2017 ◽  
Vol 28 (05) ◽  
pp. 1750030 ◽  
Author(s):  
Hiromu Tanaka
Keyword(s):  
Finite Field ◽  
Positive Characteristic ◽  
Ample Divisor ◽  
Perfect Field ◽  
Log Canonical ◽  
Canonical Pair ◽  
Field Of Positive Characteristic

Let [Formula: see text] be an [Formula: see text]-finite field containing an infinite perfect field of positive characteristic. Let [Formula: see text] be a projective log canonical pair over [Formula: see text]. In this note, we show that, for a semi-ample divisor [Formula: see text] on [Formula: see text], there exists an effective [Formula: see text]-divisor [Formula: see text] such that [Formula: see text] is log canonical if there exists a log resolution of [Formula: see text].

scholarly journals Global geometry on moduli of local systems for surfaces with boundary

2020 ◽  
Vol 156 (8) ◽  
pp. 1517-1559 ◽  
Author(s):  
Junho Peter Whang
Keyword(s):  
Moduli Space ◽  
Canonical Divisor ◽  
Local Systems ◽  
Fixed Boundary ◽  
Special Linear ◽  
Global Geometry ◽  
Nonempty Boundary ◽  
Log Canonical ◽  
Generating Series ◽  
Rank 2

AbstractWe show that every coarse moduli space, parametrizing complex special linear rank-2 local systems with fixed boundary traces on a surface with nonempty boundary, is log Calabi–Yau in that it has a normal projective compactification with trivial log canonical divisor. We connect this to a novel symmetry of generating series for counts of essential multicurves on the surface.

scholarly journals On minimal model theory for log abundant lc pairs

2020 ◽  
Vol 2020 (767) ◽  
pp. 109-159
Author(s):  
Kenta Hashizume ◽  
Zheng-Yu Hu
Keyword(s):  
Model Theory ◽  
Minimal Model ◽  
Canonical Divisor ◽  
Detailed Proof ◽  
Log Canonical

AbstractUnder the assumption of the minimal model theory for projective klt pairs of dimension n, we establish the minimal model theory for lc pairs {(X/Z,\Delta)} such that the log canonical divisor is relatively log abundant and its restriction to any lc center has relative numerical dimension at most n. We also give another detailed proof of results by the second author, and study termination of log MMP with scaling.

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