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The goal of this short note is to point out that every Fano manifold with a nef tangent bundle possesses an almost K{\"a}hler-Einstein metric, in a weak sense. The technique relies on a regularization theorem for closed positive (1,…

Complex Variables · Mathematics 2018-02-07 Jean-Pierre Demailly

We explicitly determine the optimal degenerations of Fano threefolds $X$ in family No 2.23 of Mori-Mukai's list as predicted by the Hamilton-Tian conjecture. More precisely, we find a special degeneration $(\mathcal{X}, \xi_0)$ of $X$ such…

Algebraic Geometry · Mathematics 2026-04-14 Minghao Miao , Linsheng Wang

We describe the 6-dimensional compact K-moduli space of Fano threefolds in deformation family No 2.18. These Fano threefolds are double covers of $\mathbb P^1\times\mathbb P^2$ branched along smooth $(2,2)$-surfaces, and…

Algebraic Geometry · Mathematics 2024-03-15 Kristin DeVleming , Lena Ji , Patrick Kennedy-Hunt , Ming Hao Quek

We study Fano threefolds that can be obtained by blowing up the three-dimensional projective space along a smooth curve of degree six and genus three. We produce many new K-stable examples of such threefolds, and we describe all finite…

Algebraic Geometry · Mathematics 2024-04-12 Ivan Cheltsov , Oliver Li , Sione Ma'u , Antoine Pinardin

We prove that every birationally superrigid Fano variety whose alpha invariant is greater than (resp. no smaller than) $\frac{1}{2}$ is K-stable (resp. K-semistable). We also prove that the alpha invariant of a birationally superrigid Fano…

Algebraic Geometry · Mathematics 2019-08-15 Charlie Stibitz , Ziquan Zhuang

In this paper, we study the K-stability of polarized spherical varieties. After reduction, it can be treated as a variational problem of the reduced functional of the Futaki invariant on the associated moment polytope. With the convexity…

Differential Geometry · Mathematics 2022-01-17 Yan Li , Bin Zhou

A variety is said to satisfy Condition (A) if every finite abelian subgroup of its automorphism group has a fixed point. We show that a smooth Fano 3-fold not satisfying Condition (A) is K-polystable unless it is contained in eight…

Algebraic Geometry · Mathematics 2025-05-08 Hamid Abban , Ivan Cheltsov , Takashi Kishimoto , Frederic Mangolte

We give a lower bound for the delta invariant of the fundamental divisor of a quasi-smooth weighted hypersurface. As a consequence, we prove K-stability of a large class of quasi-smooth Fano hypersurfaces of index 1 and of all smooth Fano…

Algebraic Geometry · Mathematics 2026-02-12 Taro Sano , Luca Tasin

We study slope stability of smooth surfaces and its connection with exceptional divisors. We show that a surface containing an exceptional divisor with arithmetic genus at least two is slope unstable for some polarisation. In the converse…

Algebraic Geometry · Mathematics 2008-08-06 Dmitri Panov , Julius Ross

We give a classification of Gorenstein Fano bi-equivariant compactifications of semisimple complex Lie groups with rank two, and determine which of them are equivariant K-stable and admit (singular) K\"{a}hler-Einstein metrics. As a…

Differential Geometry · Mathematics 2023-07-06 Jae-Hyouk Lee , Kyeong-Dong Park , Sungmin Yoo

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

By the description due to Mukai and Iliev, a smooth prime Fano threefold X of genus 9 is associated to a surface P(V), ruled over a smooth plane quartic Gamma. We use Kuznetsov's integral functor to study rank-2 stable sheaves on X with odd…

Algebraic Geometry · Mathematics 2014-11-03 Maria Chiara Brambilla , Daniele Faenzi

We consider Fano manifolds admitting an algebraic torus action with general orbit of codimension one. Using a recent result of Datar and Szekelyhidi, we effectively determine the existence of Kahler-Ricci solitons for those manifolds via…

Algebraic Geometry · Mathematics 2022-05-20 Nathan Ilten , Hendrik Süß

Symmetric varieties are normal equivarient open embeddings of symmetric homogeneous spaces, and they are interesting examples of spherical varieties. We prove that all smooth Fano symmetric varieties with Picard number one admit…

Algebraic Geometry · Mathematics 2021-01-08 Jae-Hyouk Lee , Kyeong-Dong Park , Sungmin Yoo

We prove that minimal instanton bundles on a Fano threefold $X$ of Picard rank one and index two are semistable objects in the Kuznetsov component $\mathsf{Ku}(X)$, with respect to the stability conditions constructed by Bayer, Lahoz,…

Algebraic Geometry · Mathematics 2023-03-23 Xuqiang Qin

We prove that all smooth Fano threefolds of rank 4 and degree 24 are K-stable.

Algebraic Geometry · Mathematics 2022-06-27 Grigory Belousov , Konstantin Loginov

We apply a recent theorem of Li and the first author to give some criteria for the K-stability of Fano varieties in terms of anticanonical Q-divisors. First, we propose a condition in terms of certain anticanonical Q-divisors of given Fano…

Algebraic Geometry · Mathematics 2016-11-01 Kento Fujita , Yuji Odaka

We prove that all general smooth Fano threefolds of Picard rank $3$ and degree $14$ are K-stable, where the generality condition is stated explicitly.

Algebraic Geometry · Mathematics 2024-05-22 Grigory Belousov , Konstantin Loginov

The main goal of this paper is to prove the polystability of the logarithmic tangent sheaf $\mathscr T_X(-D)$ of a log canonical pair $(X,D)$ whose canonical bundle $K_X+D$ is ample, generalizing in a significant way a theorem of Enoki. We…

Algebraic Geometry · Mathematics 2015-02-13 Henri Guenancia

In this paper, we investigate K-polystability on smooth complex Fano 4-folds with Lefschetz defect at least 2, focusing on the case of Lefschetz defect 3 and on Casagrande-Druel Fano 4-folds with Lefschetz defect 2. We show that exactly 5…

Algebraic Geometry · Mathematics 2025-12-16 Eleonora A. Romano , Saverio A. Secci