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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 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

In 1988, Tian posed the stabilization problem for equivariant global log canonical thresholds. We solve it in the case of toric Fano manifolds. This is the first general result on Tian's problem. A key new estimate involves expressing…

Algebraic Geometry · Mathematics 2024-03-27 Chenzi Jin , Yanir A. Rubinstein

We generalize the work of Jian Song to compute the alpha invariant of any (nef and big) toric line bundle in terms of the associated polytope. We use the analytic version of the computation of the log canonical threshold of monomial ideals…

Algebraic Geometry · Mathematics 2020-11-17 Thibaut Delcroix

We investigate the variation of log canonical thresholds in (graded) linear systems. For toric log Fano varieties, we give a sharp lower bound for log canonical thresholds of the anticanonical members in terms of the global minimal log…

Algebraic Geometry · Mathematics 2014-11-12 Florin Ambro

We relate the global log canonical threshold of a variety with torus action to the global log canonical threshold of its quotient. We apply this to certain Fano varieties and use Tian's criterion to prove the existence of Kahler-Einstein…

Algebraic Geometry · Mathematics 2013-08-13 Hendrik Süß

We study log canonical thresholds (also called global log canonical threshold or $\alpha$-invariant) of $\mathbb{R}$-linear systems. We prove existence of positive lower bounds in different settings, in particular, proving a conjecture of…

Algebraic Geometry · Mathematics 2020-12-02 Caucher Birkar

Let X be a normal complex projective variety with at worst klt singularities, and L a big line bundle on X. We use valuations to study the log canonical threshold of L, as well as another invariant, the stability threshold. The latter…

Algebraic Geometry · Mathematics 2020-02-11 Harold Blum , Mattias Jonsson

We formulate a conjecture on the number of integral points of bounded height on log Fano varieties in analogy with Manin's conjecture on the number of rational points of bounded height on Fano varieties. We also give a prediction for the…

Number Theory · Mathematics 2025-08-04 Tim Santens

Let T_n denote the set of log canonical thresholds of pairs (X,Y), with X a nonsingular variety of dimension n, and Y a nonempty closed subscheme of X. Using non-standard methods, we show that every limit of a decreasing sequence in T_n…

Algebraic Geometry · Mathematics 2009-02-02 Tommaso de Fernex , Mircea Mustata

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

We show that the global log canonical threshold of generic Fano complete intersections of index 1 and codimension $k$ in ${\mathbb P}^{M+k}$ is equal to 1 if $M\geqslant 3k+4$ and the highest degree of defining equations is at least 8. This…

Algebraic Geometry · Mathematics 2014-12-17 Thomas Eckl , Aleksandr Pukhlikov

For a smooth germ of algebraic variety $(X,0)$ and a hypersurface $(f=0)$ in $X$, with an isolated singularity at $0$, Teissier conjectured a lower bound for the Arnold exponent of $f$ in terms of the Arnold exponent of a hyperplane section…

Algebraic Geometry · Mathematics 2021-07-07 Eva Elduque , Mircea Mustata

We study log canonical thresholds on quartic threefolds, quintic fourfolds, and double spaces. As an application, we show that they have a Kaehler-Einstein metric if they are general.

Algebraic Geometry · Mathematics 2015-01-05 Ivan Cheltsov , Jihun Park , Joonyeong Won

In this paper, we compute Tian's $\alpha_{m,k}^{K\times K}$-invariant on a polarized $G$-group compactification, where $K$ denotes a maximal compact subgroup of a connected complex reductive group $G$. We prove that Tian's conjecture (see…

Differential Geometry · Mathematics 2020-06-08 Yan Li , Xiaohua Zhu

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

It is proved that the global log canonical threshold of a Zariski general Fano complete intersection of index 1 and codimension $k$ in ${\mathbb P}^{M+k}$ is equal to one, if $M\geqslant 2k+3$ and the maximum of the degrees of defining…

Algebraic Geometry · Mathematics 2017-04-04 Aleksandr V. Pukhlikov

We show that log canonical thresholds of fixed dimension are standardized. More precisely, we show that any sequence of log canonical thresholds in fixed dimension $d$ accumulates in a way which is i) either similar to how standard and…

Algebraic Geometry · Mathematics 2024-06-07 Jihao Liu , Fanjun Meng , Lingyao Xie

We show that the log canonical threshold of a generic determinantal variety and its generic link are the same.

Algebraic Geometry · Mathematics 2020-11-10 Youngsu Kim , Lance Edward Miller , Wenbo Niu

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
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