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We extend Hacon--M\textsuperscript{c}Kernan's rational chain connectedness theorem to the complex analytic setting. As a consequence, we prove that the fibers of any resolution of singularities of complex analytic kawamata log terminal…

Algebraic Geometry · Mathematics 2026-03-06 Osamu Fujino

A conic bundle is a contraction $X\to Z$ between normal varieties of relative dimension $1$ such that $-K_X$ is relatively ample. We prove a conjecture of Shokurov which predicts that, if $X\to Z$ is a conic bundle such that $X$ has…

Algebraic Geometry · Mathematics 2022-07-12 Jingjun Han , Chen Jiang , Yujie Luo

In this note, we reduce various conjectures in birational geometry, including Shokurov conjecture on singularities of the base of log Calabi-Yau fibrations of Fano type and boundedness conjecture for rationally connected Calabi-Yau…

Algebraic Geometry · Mathematics 2026-03-16 Guodu Chen , Chuyu Zhou

Shokurov conjectured that the set of all log canonical thresholds on varieties of bounded dimension satisfies the ascending chain condition. In this paper we prove that the conjecture holds for log canonical thresholds on smooth varieties…

Algebraic Geometry · Mathematics 2019-12-19 Tommaso de Fernex , Lawrence Ein , Mircea Mustata

Let $f\colon X\to Z$ be a Mori fibre space. McKernan conjectured that the singularities of $Z$ are bounded in terms of the singularities of $X$. Shokurov generalised this to pairs: let $(X,B)$ be a klt pair and $f\colon X\to Z$ a…

Algebraic Geometry · Mathematics 2012-10-10 Caucher Birkar

We establish a conjecture of Mumford characterizing rationally connected complex projective manifolds in several cases.

Algebraic Geometry · Mathematics 2017-05-05 Vladimir Lazić , Thomas Peternell

These are lectures notes on rationally connected varieties, written for the "Etats de la Recherche" of the French Mathematical Society held in Strasbourg (May 2008). We focus on geometric aspects. These notes have been written in order that…

Algebraic Geometry · Mathematics 2010-09-29 L. Bonavero

We prove a conjecture of Shokurov which characterises toric varieties using log pairs.

Algebraic Geometry · Mathematics 2018-05-23 Morgan Brown , James McKernan , Roberto Svaldi , Hong Zong

We discuss a difference between the rational and the real non-vanishing conjecture for pseudo-effective log canonical divisors of log canonical pairs. We also show the log non-vanishing theorem for rationally connected varieties under…

Algebraic Geometry · Mathematics 2012-05-30 Yoshinori Gongyo

For a birational analogue of minimal elliptic surfaces X/Y, the singularities of the fibers define a log structure in codimension one on Y. Via base change, we have a log structure in codimension one on Y', for any birational model Y' of Y.…

Algebraic Geometry · Mathematics 2007-05-23 Florin Ambro

In this paper, we investigate singularities on fibrations and related topics. We prove conjectures of McKernan and Shokurov on singularities on Fano type fibrations and a conjecture of the author on singularities on log Calabi-Yau…

Algebraic Geometry · Mathematics 2025-10-07 Caucher Birkar

Let $X$ be a projective variety with log terminal singularities and vanishing augmented irregularity. In this paper we prove that if $X$ admits a relatively minimal genus one fibration then it does contain a subvariety of codimension one…

Algebraic Geometry · Mathematics 2019-03-14 Fabrizio Anella

We verify a special case of V. V. Shokurov's conjecture about characterization of toric varieties. More precisely, let $(X,D=\sum d_iD_i)$ be a three-dimensional log variety such that $K_X+D$ is numerically trivial and $(X,D)$ has only…

Algebraic Geometry · Mathematics 2010-05-06 Yuri G. Prokhorov

We consider pairs (X,A), where X is a variety with klt singularities and A is a formal product of ideals on X with exponents in a fixed set that satisfies the Descending Chain Condition. We also assume that X has (formally) bounded…

Algebraic Geometry · Mathematics 2010-06-25 Tommaso de Fernex , Lawrence Ein , Mircea Mustata

In this short note we prove that in many cases the failure of a variety to be separably rationally connected is caused by the instability of the tangent sheaf (if there are no other obvious reasons). A simple application of the results…

Algebraic Geometry · Mathematics 2014-07-30 Zhiyu Tian

Building on results of Koll\'ar, we prove Shokurov's ACC Conjecture for log canonical thresholds on smooth varieties, and more generally, on varieties with quotient singularities.

Algebraic Geometry · Mathematics 2009-01-09 Lawrence Ein , Mircea Mustata

In this paper, we show that projective globally $F$-regular threefolds, defined over an algebraically closed field of characteristic $p\geq 11$, are rationally chain connected.

Algebraic Geometry · Mathematics 2015-05-19 Yoshinori Gongyo , Zhiyuan Li , Zsolt Patakfalvi , Karl Schwede , Hiromu Tanaka , Hong R. Zong

In this paper, the technique of foliations in characteristic $p$ is used to investigate the difference between rational connectedness and separable rational connectedness in positive characteristic. The notion of being freely rationally…

Algebraic Geometry · Mathematics 2009-10-17 Mingmin Shen

In this paper we investigate singularities on toric fibrations. In this context we study a conjecture of Shokurov (a special case of which is due to M$^\rm{c}$Kernan) which roughly says that if $(X,B)\to Z$ is an $\epsilon$-lc Fano type log…

Algebraic Geometry · Mathematics 2021-07-07 Caucher Birkar , Yifei Chen

(On the fundamental group of rationnally connected varieties.) I show that the fundamental group of a normal variety which is rationally chain connected is finite. The proof holds in non-zero characteristic. Je d\'emontre que le groupe…

Algebraic Geometry · Mathematics 2007-05-23 Antoine Chambert-Loir
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