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We prove Vojta's generalized abc conjecture for algebraic tori over function fields with exceptional sets that can be determined effectively. Additionally, we establish a version of the conjecture for toric varieties. As an application, we…

Number Theory · Mathematics 2023-10-20 Ji Guo , Khoa D. Nguyen , Chia-Liang Sun , Julie Tzu-Yueh Wang

We show that a nef line bundle on a proper scheme over an excellent base is semiample if and only if it is semiample after restricting to characteristic zero and to positive characteristic. In the process of the proof, we provide a…

Algebraic Geometry · Mathematics 2021-06-14 Jakub Witaszek

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

We prove that generic complete intersections associated to multiple mirror nef-partitions are all birational. This result solves a conjecture by Batyrev and Nill under some mild assumptions.

Algebraic Geometry · Mathematics 2016-05-17 Zhan Li

We study nonsingular branched coverings of a homogeneous space X. There is a vector bundle associated with such a covering which was conjectured by O. Debarre to be ample when the Picard number of X is one. We prove this conjecture, which…

Algebraic Geometry · Mathematics 2007-05-23 Meeyoung Kim , Laurent Manivel

Let alpha = (a,b,...) be a composition. Consider the associated poset F(alpha), called a fence, whose covering relations are x_1 < x_2 < ... < x_{a+1} > x_{a+2} > ... > x_{a+b+1} < x_{a+b+2} < ... . We study the associated distributive…

Combinatorics · Mathematics 2020-09-01 Thomas McConville , Bruce E. Sagan , Clifford Smyth

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.

Algebraic Geometry · Mathematics 2012-10-19 Salvatore Cacciola , Lorenzo Di Biagio

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

We 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 $K_X+B$ birationally…

Algebraic Geometry · Mathematics 2013-02-19 Caucher Birkar , Zhengyu Hu

The goal of this work is to study positivity of subvarieties with nef normal bundle in the sense of intersection theory. After Ottem's work on ample subschemes, we introduce the notion of a nef subscheme, which generalizes the notion of a…

Algebraic Geometry · Mathematics 2019-07-10 Chung-Ching Lau

We show that every Fell bundle B over a locally compact group G is "proper" in a sense recently introduced by Ng. Combining our results with those of Ng we show that if B satisfies the "approximation property" then it is amenable in the…

Operator Algebras · Mathematics 2007-05-23 Ruy Exel

We study the linearization of line bundles and the local structure of actions of connected linear algebraic groups, in the setting of seminormal varieties. We show that several classical results about normal varieties extend to that…

Algebraic Geometry · Mathematics 2014-10-22 Michel Brion

As a continuation of previous papers, we study the concept of a Lie algebroid structure on an affine bundle by means of the canonical immersion of the affine bundle into its bidual. We pay particular attention to the prolongation and…

Differential Geometry · Mathematics 2009-11-07 Eduardo Martinez , Tom Mestdag , Willy Sarlet

Let $P$ be the image of a period map. We discuss progress towards a conjectural Hodge theoretic completion $\overline{P}$, an analogue of the Satake-Baily-Borel compactification in the classical case. The set $\overline{P}$ is defined and…

Algebraic Geometry · Mathematics 2023-08-16 Mark Green , Phillip Griffiths , Radu Laza , Colleen Robles

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…

Algebraic Geometry · Mathematics 2013-12-03 Caucher Birkar

The main result of the paper states that a connected complex affine algebraic curve is Lipschitz normally embedded (shortened to LNE afterwards) in $\mathbb{C}^n$ if and only if its germ at any singular point is a finite union of…

Algebraic Geometry · Mathematics 2023-11-28 André Costa , Vincent Grandjean , Maria Michalska

The cohomology algebra of the canonical bundle of a compact K\"ahler manifold is naturally viewed as a module over an exterior algebra. We use the Bernstein-Gel'fand-Gel'fand correspondence, together with Generic Vanishing theory, in order…

Algebraic Geometry · Mathematics 2010-07-19 Robert Lazarsfeld , Mihnea Popa

In this paper, we study transcendental aspects of the cohomology groups of adjoint bundles of log canonical pairs, aiming to establish an analytic theory for log canonical singularities. As a result, in the case of purely log terminal…

Complex Variables · Mathematics 2020-05-12 Shin-ichi Matsumura

We describe a class (called regular) of invariant generalized complex structures on a real semisimple Lie group G. The problem reduces to the description of admissible pairs (\gk, \omega), where \gk is an appropriate regular subalgebra of…

Differential Geometry · Mathematics 2014-02-26 Dmitri V. Alekseevsky , Liana David

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…

Algebraic Geometry · Mathematics 2024-04-16 Guodu Chen , Nikolaos Tsakanikas