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We classify Fano threefolds with only Gorenstein terminal singularities and Picard number greater than 1 satisfying an additional assumption that the $G$-invariant part of the Weil divisor class group is of rank 1 with respect to an action…

Algebraic Geometry · Mathematics 2016-01-29 Yuri Prokhorov

We determine the stability/instability of the tangent bundles of the Fano varieties in a certain class of two orbit varieties, which are classified by Pasquier in 2009. As a consequence, we show that some of these varieties admit unstable…

Algebraic Geometry · Mathematics 2020-01-01 Akihiro Kanemitsu

We give a complete answer to the question of (semi)stability of tangent bundle of any nonsingular projective complex toric variety with Picard number 2 by using combinatorial crietrion of (semi)stability of an equivariant sheaf. We also…

Algebraic Geometry · Mathematics 2019-10-31 Jyoti Dasgupta , Arijit Dey , Bivas Khan

Geometric structures modeled on rational homogeneous manifolds are studied to characterize rational homogeneous manifolds and to prove their deformation rigidity. To generalize these characterizations and deformation rigidity results to…

Algebraic Geometry · Mathematics 2017-09-29 Shin-young Kim

Let $X$ be a complex smooth Fano variety of dimension $n$. In this paper, we give a classification of such $X$ when the pseudoindex is equal to $\dfrac{\dim X+1}{2}$ and the Picard number greater than one.

Algebraic Geometry · Mathematics 2024-09-23 Kiwamu Watanabe

In this paper we study mildly singular del Pezzo foliations on complex projective manifolds with Picard number one

Algebraic Geometry · Mathematics 2014-09-16 Carolina Araujo , Stéphane Druel

We show that for a weak $\mathbb{Q}$-Fano threefold $X$ ($\mathbb{Q}$-factorial with terminal singularities and $-K_X$ is nef and big) of Picard rank $\rho(X)\leq 2$, either $-K_X^3\leq 64$ or $-K_X^3=72$ and…

Algebraic Geometry · Mathematics 2025-02-28 Ching-Jui Lai , Tsung-Ju Lee

We present geometric realizations of horospherical two-orbit varieties, by showing that their blow-up along the unique closed-invariant orbit is the zero locus of a general section of a homogeneous vector bundle over some auxiliary variety.…

Algebraic Geometry · Mathematics 2020-12-11 Boris Pasquier , Laurent Manivel

We obtain the exhaustive list of 337 faithful spherical actions of rank two or less on locally factorial Fano manifolds of dimension four or less. As a preliminary step, we determine the explicit list of spherical homogeneous spaces of…

Algebraic Geometry · Mathematics 2023-08-31 Thibaut Delcroix , Pierre-Louis Montagard

Let X be a complex, Gorenstein, Q-factorial, toric Fano variety. We prove two conjectures on the maximal Picard number of X in terms of its dimension and its pseudo-index, and characterize the boundary cases. Equivalently, we determine the…

Algebraic Geometry · Mathematics 2007-05-23 C. Casagrande

A Fano variety of Picard number $1$ is said to be \textit{birationally solid} if it is not birational to a Mori fiber space over a positive dimensional base. In this paper we complete the classification of quasi-smooth birationally solid…

Algebraic Geometry · Mathematics 2023-09-12 Takuzo Okada

In this notes we classify toric Fano 4-folds having positive second Chern Character.

Algebraic Geometry · Mathematics 2011-09-06 Edilaine Ervilha Nobili

Ross and Thomas introduced the concept of slope stability to study K-stability, which has conjectural relation with the existence of constant scalar curvature K\"ahler metric. This paper presents a study of slope stability of Fano manifolds…

Algebraic Geometry · Mathematics 2014-02-26 Jun-Muk Hwang , Hosung Kim , Yongnam Lee , Jihun Park

Let X be a Fano manifold of pseudoindex i_X whose Picard number is at least two and let R be an extremal ray of X with exceptional locus Exc(R). We prove an inequality which bounds the length of R in terms of i_X and of the dimension of…

Algebraic Geometry · Mathematics 2007-05-23 Marco Andreatta , Gianluca Occhetta

We prove a more general and precise version of the Noether-Fano inequalities for birational maps between Mori fiber spaces. This is applied to give descriptions of global canonical thresholds on Fano varieties of Picard number one.

Algebraic Geometry · Mathematics 2021-03-03 Charlie Stibitz

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

Algebraic Geometry · Mathematics 2016-01-29 Yuri Prokhorov

We construct a family of examples of Legendrian subvarieties in some projective spaces. Although most of them are singular, a new example of smooth Legendrian variety in dimension 8 is in this family. The 8-fold has interesting properties:…

Algebraic Geometry · Mathematics 2010-01-20 Jaroslaw Buczynski

We classify all smooth projective horospherical varieties with Picard number 1. We prove that the automorphism group of any such variety X acts with at most two orbits and that this group still acts with only two orbits on X blown up at the…

Algebraic Geometry · Mathematics 2008-01-24 Boris Pasquier

Property $\mathcal{O}$ for an arbitrary complex, Fano manifold $X$, is a statement about the eigenvalues of the linear operator obtained from the quantum multiplication of the anticanonical class of $X$. Conjecture $\mathcal{O}$ is a…

Algebraic Geometry · Mathematics 2020-12-01 Lela Bones , Garrett Fowler , Lisa Schneider , Ryan M. Shifler

We study K-stability of smooth Fano threefolds of Picard rank $2$ and degree $22$ which can be obtained by blowing up a smooth complete intersection of two quadrics in $\mathbb{P}^5$ along a conic. We also describe the automorphism groups…