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Let $X$ be a smooth hypersurface of degree $n\geq 3$ in $\mathbb{P}^n$. We prove that the log canonical threshold of $H\in|-K_X|$ is at least $\frac{n-1}{n}$. Under the assumption of the Log minimal model program, we also prove that a…

Algebraic Geometry · Mathematics 2007-05-23 Ivan Cheltsov , Jihun Park

Let $(X,D)$ be an open log del Pezzo surface of rank one, that is, $X$ is a normal projective surface of Picard rank one, the boundary $D$ is a reduced nonzero divisor on $X$, and the anti-log canonical divisor $-(K_X+D)$ is ample. We show…

Algebraic Geometry · Mathematics 2025-08-20 Karol Palka , Tomasz Pełka

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

We give an explicit formula for the log-canonical threshold of a reduced germ of plane curve. The formula depends only on the first two maximal contact values of the branches and their intersection multiplicities. We also improve the two…

Algebraic Geometry · Mathematics 2016-04-06 C. Galindo , F. Hernando , F. Monserrat

This paper proposes a Fujita-type freeness conjecture for semi-log canonical pairs. We prove it for curves and surfaces by using the theory of quasi-log schemes and give some effective very ampleness results for stable surfaces and semi-log…

Algebraic Geometry · Mathematics 2017-01-26 Osamu Fujino

We compute the log canonical thresholds of non-negatively curved singular hermitian metrics on ample linearized line bundles on bi-equivariant group compactifications of complex reductive groups. To this end, we associate to any such metric…

Algebraic Geometry · Mathematics 2020-09-16 Thibaut Delcroix

In this paper, we show the log canonical threshold values of the surfaces which has du Val type singularities.These surfaces can be interpreted as statistical or machine learning models. The results of $A_n, D_n, E_6, E_7$ and $E_8$ are…

Algebraic Geometry · Mathematics 2023-12-29 Yoshinori Watanabe

We prove a conjecture due to V.V. Shokurov on the boundedness of $\epsilon$-log canonical complements on surfaces. As an application we give a new proof to the boundedness of weak log Fano surfaces.

Algebraic Geometry · Mathematics 2007-05-23 Caucher Birkar

This is an expanded version of our work [AN88], 1988, in Russian. We classify del Pezzo surfaces over C with log terminal singularities of index \le 2. By classification, we understand a description of the intersection graph of all…

Algebraic Geometry · Mathematics 2007-05-23 Valery Alexeev , Viacheslav V. Nikulin

We prove that if Y is a hypersurface of degree d in P^n with isolated singularities, then the log canonical threshold of (P^n,Y) is at least min{n/d,1}. Moreover, if d is at least n+1, then we have equality if and only if Y is the…

Algebraic Geometry · Mathematics 2007-05-23 Lawrence Ein , Mircea Mustata

We study log canonical models of foliated surfaces of general type. In particular, we show that log canonical models of general type and their minimal partial du Val resolutions are bounded. Moreover, we show the valuative criteria of…

Algebraic Geometry · Mathematics 2022-02-25 Yen-An Chen

We show Fujita's spectrum conjecture for $\epsilon$-log canonical pairs and Fujita's log spectrum conjecture for log canonical pairs. Then, we generalize the pseudo-effective threshold of a single divisor to multiple divisors and establish…

Algebraic Geometry · Mathematics 2017-06-21 Jingjun Han , Zhan Li

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 consider log del Pezzo surfaces coming with a non-trivial torus action. Such a surface is 1/k-log canonical if it allows a resolution of singularities with discrepanies all greater or equal to 1/k-1. We provide a concrete classification…

Algebraic Geometry · Mathematics 2025-06-10 Daniel Haettig , Juergen Hausen , Justus Springer

There are several variations of the definition of log del Pezzo pairs in the literature. We define their suitable smooth models, and we show that they are the same. In particular, we obtain a characterization of smooth log del Pezzo pairs…

Algebraic Geometry · Mathematics 2013-04-25 DongSeon Hwang , Jinhyung Park

We give upper bounds for the number of rational points of bounded anti-canonical height on del Pezzo surfaces of degree at most five over any global field whose characteristic is not equal to two or three. For number fields these results…

Number Theory · Mathematics 2024-01-11 Jakob Glas , Leonhard Hochfilzer

In the paper we compute the global log canonical thresholds of the secondary Burniat surfaces with $K^2 = 5$. Furthermore, we establish optimal lower bounds for the log canonical thresholds of members in pluricanonical sublinear systems of…

Algebraic Geometry · Mathematics 2024-01-10 Nguyen Bin , Jheng-Jie Chen , YongJoo Shin

The delta invariant interprets the criterion for the K-(poly)stability of log terminal Fano varieties. In this paper, we determine the whole local delta invariant for all weak del Pezzo surfaces with the anti-canonical degree $\geq 5$.

Algebraic Geometry · Mathematics 2025-04-02 Hiroto Akaike

This paper shows that Mustata-Nakamura's conjecture holds for pairs consisting of a smooth surface and a multiideal with a real exponent over the base field of positive characteristic. As corollaries, we obtain the ascending chain condition…

Algebraic Geometry · Mathematics 2020-03-11 Shihoko Ishii

It was conjectured by Tian that the global log canonical threshold (known as the $\alpha$-invariant) is equal to the level $k$ log canonical threshold (known as the $\alpha_k$-invariant) for all sufficiently large $k$. A weaker folklore…

Algebraic Geometry · Mathematics 2024-12-04 Chenzi Jin