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We prove a product formula for $\delta$-invariant and as an application, we show that product of K-(semi, poly)stable Fano varieties is also K-(semi, poly)stable.

Algebraic Geometry · Mathematics 2021-02-22 Ziquan Zhuang

We study K-stability of products of K-stable $\mathbb{Q}$-Fano varieties.

Algebraic Geometry · Mathematics 2016-10-18 Jihun Park , Joonyeong Won

For a variety $X$, a big $\mathbb{Q}$-divisor $L$ and a closed connected subgroup $G \subset \mathrm{Aut}(X, L)$ we define a $G$-invariant version of the $\delta$-threshold. We prove that for a Fano variety $(X, -K_X)$ and a connected…

Algebraic Geometry · Mathematics 2020-08-27 Aleksei Golota

We provide a sufficient condition for polarisations of Fano varieties to be K-stable in terms of Tian's alpha invariant, which uses the log canonical threshold to measure singularities of divisors in the linear system associated to the…

Algebraic Geometry · Mathematics 2016-04-21 Ruadhaí Dervan

We present an elementary way of recovering a well-known criterion of K-stability for Fano reductive group compactifications.

Algebraic Geometry · Mathematics 2025-02-19 Gabriella Clemente

In 1987, the $\alpha$-invariant theorem gave a fundamental criterion for existence of Kahler-Einstein metrics on smooth Fano manifolds. In 2012, Odaka-Sano extended the framework to $\mathbb{Q}$-Fano varieties in terms of K-stability, and…

Differential Geometry · Mathematics 2025-01-31 Chenzi Jin , Yanir A. Rubinstein , Gang Tian

Fujita and Li have given a characterisation of K-stability of a Fano variety in terms of quantities associated to valuations, which has been essential to all recent progress in the area. We introduce a notion of valuative stability for…

Algebraic Geometry · Mathematics 2021-09-23 Ruadhaí Dervan , Eveline Legendre

We develop a general approach to prove K-stability of Fano varieties. The new theory is used to (a) prove the existence of K\"ahler-Einstein metrics on all smooth Fano hypersurfaces of Fano index two, (b) to compute the stability thresholds…

Algebraic Geometry · Mathematics 2022-06-15 Hamid Abban , Ziquan Zhuang

We give a lower bound of the $\delta$-invariants of ample line bundles in terms of Seshadri constants. As applications, we prove the uniform K-stability of infinitely many families of Fano hypersurfaces of arbitrarily large index, as well…

Algebraic Geometry · Mathematics 2022-04-28 Hamid Abban , Ziquan Zhuang

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 settle the problem of K-stability of quasi-smooth Fano 3-fold hypersurfaces with Fano index 1 by providing lower bounds for their delta invariants. We use the method introduced by Abban and Zhuang for computing lower bounds of delta…

Algebraic Geometry · Mathematics 2026-05-27 Livia Campo , Takuzo Okada

Using log canonical thresholds and basis divisors Fujita--Odaka introduced purely algebro-geometric invariants $\delta_m$ whose limit in $m$ is now known to characterize uniform K-stability on a Fano variety. As shown by Blum-Jonsson this…

Differential Geometry · Mathematics 2024-11-20 Yanir A. Rubinstein , Gang Tian , Kewei Zhang

Let $X \subset \mathbb P(a_0,\ldots,a_n)$ be a quasi-smooth weighted Fano hypersurface of degree $d$ and index $I_X$ such that $a_i |d$ for all $i$, with $a_0 \le \ldots \le a_n$. If $I_X=1$, we show that, under a suitable condition, the…

Algebraic Geometry · Mathematics 2024-01-24 Taro Sano , Luca Tasin

We define G-pseudovaluations on a variety with a group action G. By introducing G-pseudovaluations, we are able to give some criteria for G-equivariant K-stability of Fano varieties which are parallel to existing results for usual…

Algebraic Geometry · Mathematics 2020-07-31 Ziwen Zhu

Tian's criterion for K-stability states that a Fano variety of dimension $n$ whose alpha invariant is greater than $\frac{n}{n+1}$ is K-stable. We show that this criterion is sharp by constructing singular Fano varieties with alpha…

Algebraic Geometry · Mathematics 2020-08-06 Yuchen Liu , Ziquan Zhuang

We prove some criteria for uniform K-stability of log Fano pairs. In particular, we show that uniform K-stability is equivalent to $\beta$-invariant having a positive lower bound. Then we study the relation between optimal destabilization…

Algebraic Geometry · Mathematics 2025-01-06 Chuyu Zhou , Ziquan Zhuang

We characterize the situations in which certain accumulation properties of topological spaces are preserved under taking products.

General Topology · Mathematics 2011-06-14 Paolo Lipparini

We introduce a notion of K-stability for adjoint foliated structures via test configurations and the foliated Donaldson-Futaki invariant. We prove reduction to special test configurations for adjoint Fano foliated structures by showing that…

Algebraic Geometry · Mathematics 2026-05-22 Theodoros Stylianos Papazachariou

Generalizing Fujita-Odaka invariant, we define a function $\tilde{\delta}$ on a set of generalized $b$-divisors over a smooth Fano variety. This allows us to provide a new characterization of uniform $K$-stability. A key role is played by a…

Algebraic Geometry · Mathematics 2023-04-27 Antonio Trusiani

We show that uniform K-stability is a Zariski open condition in Q-Gorenstein families of Q-Fano varieties. To prove this result, we consider the behavior of the stability threshold in families. The stability threshold (also known as the…

Algebraic Geometry · Mathematics 2020-06-11 Harold Blum , Yuchen Liu
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