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Let $G = GL(n)$ and $K = GL(p) \times GL(q)$ with $p+q=n$, where the groups are taken over $\C$. In this paper we study a certain family of $K$-orbit closures on the flag variety $X$ of $G$. The geometry of these orbit closures plays a…

Algebraic Geometry · Mathematics 2026-03-31 William Graham , Minyoung Jeon , Scott Joseph Larson

Let S be an arbitrary real surface, with or without boundary, contained in a hypersurface M of the complex euclidean space \C^2, with S and M of class C^{2, a}, where 0 < a < 1. If M is globally minimal, if S is totally real except at…

Complex Variables · Mathematics 2009-09-29 Joël Merker , Egmont Porten

Let M^7 a manifold with holonomy in G_2, and Y^3 an associative submanifold with boundary in a coassociative submanifold. In [5], the authors proved that M_{X,Y}, the moduli space of its associative deformations with boundary in the fixed…

Differential Geometry · Mathematics 2009-11-19 Damien Gayet

In this paper, for compact K\"ahler manifolds with nef cotangent bundle, we study the abundance conjecture and the associated Iitaka fibrations. We show that, for a minimal compact K\"ahler manifold, the second Chern class vanishes if and…

Algebraic Geometry · Mathematics 2022-05-24 Masataka Iwai , Shin-ichi Matsumura

In this paper, we prove that, a compact complex manifold $X$ admits a smooth Hermitian metric with positive (resp. negative) scalar curvature if and only if $K_X$ (resp. $K_X^{-1}$) is not pseudo-effective. On the contrary, we also show…

Differential Geometry · Mathematics 2017-10-12 Xiaokui Yang

We prove that Chern classes in continuous $\ell$-adic cohomology of automorphic bundles associated to representations of $G$ on a projective Shimura variety with data $(G,X)$ are trivial rationally. It is a consequence of Beilinson's…

Algebraic Geometry · Mathematics 2017-02-01 Hélène Esnault , Michael Harris

Following a suggestion made by J.-P. Demailly, for each $k\ge 1$, we endow, by an induction process, the $k$-th (anti)tautological line bundle $\mathcal O_{X_k}(1)$ of an arbitrary complex directed manifold $(X,V)$ with a natural smooth…

Differential Geometry · Mathematics 2017-04-04 Simone Diverio

In this paper, we prove a special case of Campana--Peternell's conjecture in dimension 4. Specifically, we show that a projective smooth fourfold $X$ with $c^2_1(X)\cdot c_2(X)\neq 0$ and strictly nef anti-canonical divisor $-K_X$ is a Fano…

Algebraic Geometry · Mathematics 2023-05-10 Haidong Liu

It known from the work of Feigin-Tsygan, Weibel and Keller that the cohomology groups of a smooth complex variety X can be recovered from (roughly speaking) its derived category of coherent sheaves. In this paper we show that for a finite…

Algebraic Geometry · Mathematics 2007-05-23 Vladimir Baranovsky

In a recent work, Kai Tang conjectured that any compact Hermitian manifold with non-zero constant mixed curvature must be K\"ahler. He confirmed the conjecture in complex dimension $2$ and for Chern K\"ahler-like manifolds in general…

Differential Geometry · Mathematics 2025-10-14 Shuwen Chen , Fangyang Zheng

A well known conjecture in complex geometry states that a compact Hermitian manifold with constant holomorphic sectional curvature must be K\"ahler if the constant is non-zero and must be Chern flat if the constant is zero. The conjecture…

Differential Geometry · Mathematics 2022-07-18 Yulu Li , Fangyang Zheng

We prove that the cone of mobile divisors and the cone of curves birationally movable in codimension 1 are dual in the $(K+B)$-negative part for a klt pair $(X/Z,B)$. We also prove the structure theorem and the contraction theorem for the…

Algebraic Geometry · Mathematics 2011-05-10 Sung Rak Choi

In this paper, we prove that for a threefold of Fano type $X$ and a movable $\mathbb{Q}$-Cartier Weil divisor $D$ on $X$, the number of smooth varieties that arise during the running of a $D$-MMP is bounded by $1 + h^1(X, 2D)$.…

Algebraic Geometry · Mathematics 2025-11-13 Donghyeon Kim

Motivic Chern classes are elements in the K-theory of an algebraic variety $X$, depending on an extra parameter $y$. They are determined by functoriality and a normalization property for smooth $X$. In this paper we calculate the motivic…

Algebraic Geometry · Mathematics 2025-04-02 Paolo Aluffi , Leonardo C. Mihalcea , Jörg Schürmann , Changjian Su

We show that Ambro-Kawamata's non-vanishing conjecture holds true for a quasi-smooth WCI X which is Fano or Calabi-Yau, i.e. we prove that, if H is an ample Cartier divisor on X, then |H| is not empty. If X is smooth, we further show that…

Algebraic Geometry · Mathematics 2018-03-16 Marco Pizzato , Taro Sano , Luca Tasin

Let $X$ be a minimal projective Gorenstein 3-fold of general type. We give two applications of an inequality between $\chi (\omega_X)$ and $p_g(X)$: 1) Assume that the canonical map $\Phi_{|K_X|}$ is of fiber type. Let $F$ be a smooth model…

Algebraic Geometry · Mathematics 2007-05-23 Meng Chen , Christopher D. Hacon

Let (X,D) be a dlt pair, where X is a normal projective variety. Let S denote the support of the rounddown of D, and K the canonical divisor of X. We show that any smooth family of canonically polarized varieties over X\S is isotrivial if…

Algebraic Geometry · Mathematics 2019-02-20 Daniel Lohmann

We prove an extension theorem for effective plt pairs $(X,S+B)$ of non-negative Kodaira dimension $\kappa (K_X+S+B)\geq 0$. The main new ingredient is a refinement of the Ohsawa-Takegoshi $L^2$ extension theorem involving singular hermitian…

Algebraic Geometry · Mathematics 2010-12-22 Jean-Pierre Demailly , Christopher D. Hacon , Mihai Paun

In this paper, we prove the Novikov conjecture for a class of highly non-linear groups, namely discrete subgroups of the diffeomorphism group of a compact smooth manifold. This removes the volume-preserving condition in a previous work.…

K-Theory and Homology · Mathematics 2025-02-24 Sherry Gong , Jianchao Wu , Zhizhang Xie , Guoliang Yu

In this article we prove the existence of pl-flipping and divisorial contractions and pl flips in dimension $n$ for compact K\"ahler varieties, assuming results of the minimal model program in dimension $n-1$. We also give a self contained…

Algebraic Geometry · Mathematics 2024-06-27 Omprokash Das , Christopher Hacon