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We show that any $n$-dimensional Fano manifold $X$ admitting K\"ahler-Einstein metrics satisfies that the anti-canonical volume is less than or equal to the value $(n+1)^n$. Moreover, the equality holds if and only if $X$ is isomorphic to…

代数几何 · 数学 2015-08-20 Kento Fujita

The Ap\'ery numbers of Fano varieties are asymptotic invariants of their quantum differential equations. In this paper, we initiate a program to exhibit these invariants as (mirror to) limiting extension classes of higher cycles on the…

代数几何 · 数学 2024-02-21 Vasily Golyshev , Matt Kerr , Tokio Sasaki

The Abundance conjecture predicts that on a minimal projective klt pair $(X,\Delta)$, the adjoint divisor $K_X+\Delta$ is semiample. When $\chi(X,\mathcal O_X)\neq0$, we give a necessary and sufficient condition for the conjecture to hold…

代数几何 · 数学 2024-06-27 Vladimir Lazić

Strong asymptotics on the whole complex plane of a sequence of monic Jacobi polynomials $P_n^{(\alpha_n, \beta_n)}$ is studied, assuming that $$ \lim_{n\to\infty} \frac{\alpha_n}{n}=A, \qquad \lim_{n\to\infty} \frac{\beta _n}{n}=B, $$ with…

经典分析与常微分方程 · 数学 2007-05-23 A. B. J. Kuijlaars , A. Martinez-Finkelshtein

Let $X$ be a variety with at most terminal $\mathbb Q$-factorial singularities of dimension $n$. We study local contractions $f:X\to Z$ supported by a $\mathbb Q$-Cartier divisor of the type $K_X+ \tau L$, where $L$ is an $f$-ample Cartier…

代数几何 · 数学 2015-04-24 Marco Andreatta , Luca Tasin

We prove that the stability condition for Fano manifolds defined by Saito-Takahashi, given in terms of the sum of the Ding invariant and the Chow weight, is equivalent to the existence of anticanonically balanced metrics. Combined with the…

微分几何 · 数学 2024-01-18 Yoshinori Hashimoto

Let $X$ be a very general hypersurface of degree $d$ in the projective $(n+1)$-space with $n \ge 3$, and $f: X \to Y$ a non-birational surjective morphism to a normal projective variety $Y$. We first prove that $Y$ is a klt Fano variety if…

代数几何 · 数学 2025-08-26 Yongnam Lee , Yujie Luo , De-Qi Zhang

We investigate the relationship between the Fano type property on fibers over a Zariski dense subset and the global Fano type property. We establish the invariance of N\'eron-Severi spaces, nef cones, effective cones, movable cones, and…

代数几何 · 数学 2026-01-27 Sung Rak Choi , Zhan Li , Chuyu Zhou

We study the cones of q-ample divisors on smooth complex varieties. In favourable cases, we identify a part where the closure of this cone and the nef cone have the same boundary. This is especially interesting for Fano (or almost Fano)…

代数几何 · 数学 2016-02-17 Robert Laterveer

We study the anti-canonical ring of a projective variety and we characterise varieties of log Fano type depending on the singularities of these models.

代数几何 · 数学 2013-08-19 Paolo Cascini , Yoshinori Gongyo

In this article we prove that if $(X,B+\beta)$ is a projective generalized klt pair such that $B+\beta$ is big, then $(X,B+\beta)$ admits a good Minimal Model or Mori fiber space. In particular, this implies Tossati's transcendental…

代数几何 · 数学 2024-12-11 Omprokash Das , Christopher Hacon

We classify log-canonical pairs $(X, \Delta)$ of dimension two with $K_X+\Delta$ an ample Cartier divisor with $(K_X+\Delta)^2=1$, giving some applications to stable surfaces with $K^2=1$. A rough classification is also given in the case…

代数几何 · 数学 2015-08-19 Marco Franciosi , Rita Pardini , Sönke Rollenske

The 'moduli continuity method' permits an explicit algebraisation of the Gromov-Hausdorff compactification of K\"ahler-Einstein metrics on Fano manifolds in some fundamental examples. In this paper, we apply such method in the 'log setting'…

代数几何 · 数学 2020-11-11 Patricio Gallardo , Jesus Martinez-Garcia , Cristiano Spotti

For lc algebraically integrable foliations on klt varieties, we prove the base-point-freeness theorem, the contraction theorem, and the existence of flips. The first result resolves a conjecture of Cascini and Spicer, while the latter two…

代数几何 · 数学 2025-06-09 Jihao Liu , Fanjun Meng , Lingyao Xie

We show that the augmented base locus coincides with the exceptional locus (i.e. null locus) for any nef $\mathbb{R}$-Cartier divisor on any scheme projective over a field (of any characteristic). Next we prove a semi-ampleness criterion in…

代数几何 · 数学 2013-12-03 Caucher Birkar

Given a fibration over a perfect field of positive characteristic, we study an Iitaka-type inequality for the anticanonical divisors. We conclude that it holds when the source of the fibration is a threefold or when the target is a curve,…

代数几何 · 数学 2026-03-27 Marta Benozzo

We show that if a Fano manifold has discrete automorphism group and admits a polarized K\"ahler-Einstein metric, then there exists a sequence of anticanonically balanced metrics converging smoothly to the K\"ahler-Einstein metric. Our proof…

微分几何 · 数学 2022-04-27 Louis Ioos

In a decision-theoretic framework, the minimax lower bound provides the worst-case performance of estimators relative to a given class of statistical models. For parametric and semiparametric models, the H\'{a}jek--Le Cam local asymptotic…

统计理论 · 数学 2024-10-22 Kenta Takatsu , Arun Kumar Kuchibhotla

The geometry of the Fano scheme of maximal linear spaces contained in the base locus of a pencil of quadrics has been studied by algebraic geometers when the base field is algebraically closed. In this paper, we work over an arbitrary base…

代数几何 · 数学 2013-02-12 Xiaoheng Wang

We approach non-divisorial base loci of big and nef line bundles on irreducible symplectic varieties. While for K3 surfaces, only divisorial base loci can occur, nothing was known about the behaviour of non-divisorial base loci for more…

代数几何 · 数学 2019-01-24 Ulrike Riess