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We study Q-Fano threefolds of large Fano index. In particular, we prove that the maximum of Fano index is attained for the weighted projective space P(3,4,5,7).

Algebraic Geometry · Mathematics 2011-01-18 Yuri Prokhorov

We show that a non-toric $\mathbb{Q}$-factorial terminal Fano threefold of Picard rank $1$ and Fano index $13$ is a weighted hypersurface of degree $12$ in $\mathbb{P}(3,4,5,6,7)$.

Algebraic Geometry · Mathematics 2026-01-22 Yuri Prokhorov

We show that the anti-canonical volume of a canonical weak Fano $3$-fold is at most $72$. This upper bound is optimal.

Algebraic Geometry · Mathematics 2025-10-09 Chen Jiang , Tianqi Zhang , Yu Zou

This paper considers Q-Fano 3-folds X with \rho=1. The aim is to determine the maximal Fano index f of X. We prove that f<= 19, and that in case of equality, the Hilbert series of X equals that of weighted projective space PP(3,4,5,7). From…

Algebraic Geometry · Mathematics 2007-05-23 Kaori Suzuki

We show that the $\mathbb{Q}$-Fano index of a canonical weak Fano $3$-fold is at most $66$. This upper bound is optimal and gives an affirmative answer to a conjecture of Chengxi Wang in dimension $3$. During the proof, we establish a new…

Algebraic Geometry · Mathematics 2025-10-21 Chen Jiang , Haidong Liu

We classify Q-Fano threefolds of Fano index > 2 and big degree.

Algebraic Geometry · Mathematics 2016-01-29 Yuri Prokhorov

We prove the Shafarevich conjecture for Fano threefolds of Picard rank 1, index 1 and degree 4.

Algebraic Geometry · Mathematics 2022-07-13 Philipp Licht

It was proved by J.~A.~Chen and M.~Chen that a terminal Fano $3$-fold $X$ satisfies $(-K_X)^3\geq \frac{1}{330}$. We show that a $\mathbb{Q}$-factorial terminal Fano $3$-fold $X$ with $\rho(X)=1$ and $(-K_X)^3=\frac{1}{330}$ is a weighted…

Algebraic Geometry · Mathematics 2025-05-08 Chen Jiang

For a Fano manifold of pseudo-index at least 3 and $c_1^2-2c_2$ nef, we show irreducibility of certain spaces of curves on the Fano manifold implies the manifold is a union of rational surfaces.

Algebraic Geometry · Mathematics 2007-05-23 A. J. de Jong , Jason Michael Starr

In this note we illustrate the Fanosearch programme of Coates, Corti, Galkin, Golyshev, and Kasprzyk in the example of the anticanonical cone over the smooth del Pezzo surface of degree 6.

Algebraic Geometry · Mathematics 2019-01-21 Andrea Petracci

We show that for a $\mathbb Q$-factorial canonical Fano $3$-fold $X$ of Picard number $1$, $(-K_X)^3\leq 72$. The main tool is a Kawamata--Miyaoka type inequality which relates $(-K_X)^3$ with $\hat{c}_2(X)\cdot c_1(X)$, where…

Algebraic Geometry · Mathematics 2025-11-20 Chen Jiang , Haidong Liu , Jie Liu

The map given by the anticanonical bundle of a Fano manifold is investigated with respect to a number of natural notions of higher order embeddings of projective manifolds. This is of importance in the understanding of higher order…

alg-geom · Mathematics 2007-05-23 M. C. Beltrametti , S. Di Rocco , A. J. Sommese

We determine the complete list of anticanonically embedded quasi smooth log Fano 3-folds in weighted projective 4-spaces. This implies that the Reid-Fletcher list of 95 types of anticanonically embedded quasi smooth terminal Fano threefolds…

Algebraic Geometry · Mathematics 2007-05-23 Jennifer M. Johnson , János Kollár

We consider Fano threefolds $X$ with canonical Gorenstein singularities. Under additional assumption that $X$ has at least one non-cDV point we prove a sharp bound of the degree: $-K_X^3\le 72$.

Algebraic Geometry · Mathematics 2010-05-12 Yuri G. Prokhorov

We compute global log canonical thresholds of certain birationally bi-rigid Fano 3-folds embedded in weighted projective spaces as complete intersections of codimension 2 and prove that they admit an orbifold K\"{a}hler-Einstein metric and…

Algebraic Geometry · Mathematics 2019-03-19 In-Kyun Kim , Takuzo Okada , Joonyeong Won

The goal of these lecture notes is to present the modern point of view on the classification of Fano threefolds. We tried to offer a self-consistent treatment of the topics covered. \par\medskip\noindent These notes have been published in…

Algebraic Geometry · Mathematics 2025-12-02 Yuri Prokhorov

We compute global log canonical thresholds, or equivalently alpha invariants, of birationally rigid orbifold Fano threefolds embedded in weighted projective spaces as codimension two or three. As an important application, we prove that most…

Algebraic Geometry · Mathematics 2016-04-04 In-Kyun Kim , Takuzo Okada , Joonyeong Won

We consider Fano threefolds $V$ with canonical Gorenstein singularities. A sharp bound $-K_V^3\le 72$ of the degree is proved.

Algebraic Geometry · Mathematics 2025-11-26 Yuri G. Prokhorov

Let $U\subset \mathbb P^N$ be a projective variety which is not a cone and whose hyperplane sections are smooth Enriques surfaces. We prove that the degree of a $U$ is at most 32 and the bound is sharp.

Algebraic Geometry · Mathematics 2015-06-26 Yuri Prokhorov

In this paper we prove that any smooth prime Fano threefold, different from the Mukai-Umemura threefold, contains a 1-dimensional family of intersecting lines. Combined with a result of the second author (see J. Algebr. Geom. 8:2 (1999),…

Algebraic Geometry · Mathematics 2007-05-23 Atanas Iliev , Carmen Schuhmann
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