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

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

We show that every quasihyperbolic geodesic in a John space admitting a roughly starlike Gromov hyperbolic quasihyperbolization is a cone arc. This result provides a new approach to the elementary metric geometry question, formulated in…

Complex Variables · Mathematics 2019-12-24 Qingshan Zhou , Yaxiang Li , Antti Rasila

A complex projective manifold is rationally connected, resp. rationally simply connected, if finite subsets are connected by a rational curve, resp. the spaces parameterizing these connecting rational curves are themselves rationally…

Algebraic Geometry · Mathematics 2017-06-20 Jason Starr , Chenyang Xu

Let $(X,\Delta)$ be a normal pair with a projective morphism $X \to Z$ and let $A$ be a relatively ample $\mathbb{R}$-divisor on $X$. We prove the termination of some minimal model program on $(X,\Delta+A)/Z$ and the abundance conjecture…

Algebraic Geometry · Mathematics 2025-10-21 Kenta Hashizume

We prove that, assuming the F-conjecture, the log canonical model of the pair $(\bar{M}_{0,n}, \sum a_i \psi_i)$ is the Hassett's moduli space of weighted pointed stable rational curves without any modification of weight coefficients. For…

Algebraic Geometry · Mathematics 2010-11-18 Han-Bom Moon

Let $f:X\to U$ be a projective morphism of normal varieties and $(X,\Delta)$ a dlt pair. We prove that if there is an open set $U^0\subset U$, such that $(X,\Delta)\times_U U^0$ has a good minimal model over $U^0$ and the images of all the…

Algebraic Geometry · Mathematics 2012-06-29 Christopher D. Hacon , Chenyang Xu

Let $C$ be a smooth projective curve over $\mathbb C$. Let $n,d\geq 1$. Let $\mathcal Q$ be the Quot scheme parameterizing torsion quotients of the vector bundle $\mathcal O^n_C$ of degree $d$. In this article we study the nef cone of…

Algebraic Geometry · Mathematics 2020-07-02 Chandranandan Gangopadhyay , Ronnie Sebastian

We identify a set of initial rational contractions of fiber type on $\overline{M}_{0,6}$. Our proof uses a new algorithm we develop for verifying descriptions of the cone of effective divisors on varieties without elementary rational…

Algebraic Geometry · Mathematics 2022-09-28 Eric Jovinelly

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

An endomorphism $f$ of a projective variety X is polarized (resp. quasi-polarized) if $f^*H$ is linearly equivalent to $qH$ for some ample (resp. nef and big) Cartier divisor $H$ and integer $q > 1$. First, we use cone analysis to show that…

Algebraic Geometry · Mathematics 2018-09-24 Sheng Meng , De-Qi Zhang

In the first part of this article, we study linear cones over totally ordered fields. We show that for each such cone there uniquely exists a universal vector space (called its spanned vector space) into which it embeds as a generating…

Metric Geometry · Mathematics 2025-08-26 Ethan Kharitonov , Argam Ohanyan

We show that cubulated hyperbolic groups with spherical boundary of dimension 3 or at least 5 are virtually fundamental groups of closed, orientable, aspherical manifolds, provided that there are sufficiently many quasi-convex,…

Geometric Topology · Mathematics 2024-06-14 Corey Bregman , Merlin Incerti-Medici

We prove the cone theorem for varieties with LCIQ singularities using deformation theory of stable maps into Deligne-Mumford stacks. We also obtain a sharper bound on $-(K_X+D)$-degree of $(K_X+D)$-negative extremal rays for projective…

Algebraic Geometry · Mathematics 2009-08-20 Jiun-Cheng Chen , Hsian-Hua Tseng

It is well known that a smooth projective Fano variety is rationally connected. Recently Zhang (and later Hacon and McKernan as a special case of their work on the Shokurov RC-conjecture) proved that the same conclusion holds for a klt pair…

Algebraic Geometry · Mathematics 2009-01-29 Amaël Broustet , Gianluca Pacienza

We establish normal form theorems for a large class of singular flat connections on complex manifolds, including connections with logarithmic poles along weighted homogeneous Saito free divisors. As a result, we show that the moduli spaces…

Algebraic Geometry · Mathematics 2022-09-02 Francis Bischoff

In this paper, we show that the canonical divisor of a smooth toroidal compactification of a complex hyperbolic manifold must be nef if the dimension is greater or equal to three. Moreover, if $n\geq 3$ we show that the numerical dimension…

Algebraic Geometry · Mathematics 2017-10-17 Gabriele Di Cerbo , Luca F. Di Cerbo

In this paper we give a complete description of the irreducible components of the jet schemes (with origin in the singular locus) of a two-dimensional quasi-ordinary hypersurface singularity. We associate with these components and with…

Algebraic Geometry · Mathematics 2021-07-01 Helena Cobo , Hussein Mourtada

In this paper, we present a general wall crossing theory for K-stability and K-moduli of log Fano pairs whose boundary divisors can be non-proportional to the anti-canonical divisor. Along the way, we prove that there are only finitely many…

Algebraic Geometry · Mathematics 2026-04-14 Yuchen Liu , Chuyu Zhou

We propose conjectural semiorthogonal decompositions for Fano schemes of linear subspaces on intersections of two quadrics, in terms of symmetric powers of the associated hyperelliptic (resp. stacky) curve. When the intersection is…

We prove some results on effective very ampleness and projective normality for some varieties with trivial canonical bundle. In the first part we prove an effective projective normality result for an ample line bundle on regular smooth…

Algebraic Geometry · Mathematics 2019-10-01 Jayan Mukherjee , Debaditya Raychaudhury