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We study complex compact Kaehler manifolds $X$ carrying a contact structure. If $X$ is almost homogeneous and $b_2(X) \geq 2$, then $X$ is a projectivised tangent bundle (this was known in the projective case even without assumption on the…

Algebraic Geometry · Mathematics 2012-10-08 Thomas Peternell , Florian Schrack

We prove the classical Yano-Obata conjecture by showing that the connected component of the group of holomorph-projective transformations of a closed, connected Riemannian K\"ahler manifold consists of isometries unless the metric has…

Differential Geometry · Mathematics 2015-10-07 Vladimir S. Matveev , Stefan Rosemann

In this paper, we prove that if a compact K\"ahler manifold $X$ has a smooth Hermitian metric $\omega$ such that $(T_X,\omega)$ is uniformly RC-positive, then $X$ is projective and rationally connected. Conversely, we show that, if a…

Algebraic Geometry · Mathematics 2020-11-18 Xiaokui Yang

Let X be a compact K\"ahler manifold such that the universal cover admits a compactification. We conjecture that the fundamental group is almost abelian and reduce it to a classical conjecture of Iitaka.

Algebraic Geometry · Mathematics 2014-10-13 Benoît Claudon , Andreas Hoering

In this paper we confirm a folklore conjecture which suggests that for a complete noncompact manifold $M$ of finite volume with sectional curvature $-1 \leq K \leq 0$, if the universal cover of $M$ is a visibility manifold, then the…

Geometric Topology · Mathematics 2024-05-30 Ran Ji , Yunhui Wu

We consider 6-dimensional strict nearly Kaehler manifolds acted on by a compact, cohomogeneity one automorphism group G. We classify the compact manifolds of this class up to G-diffeomorphisms. We also prove that the manifold has constant…

Differential Geometry · Mathematics 2015-05-13 Fabio Podesta' , Andrea Spiro

We show that almost nonnegatively curved m-dimensional manifolds are, up to finite cover, nilpotent spaces in the sense of homotopy theory and have C(m)-nilpotent fundamental groups. We also show that up to a finite cover almost…

Differential Geometry · Mathematics 2019-05-21 Vitali Kapovitch , Anton Petrunin , Wilderich Tuschmann

The expression (-1/u) times the Hessian of u transforms as a symmetric (0,2) tensor under projective coordinate transformations, so long as u transforms as a section of a certain line bundle. On a locally projectively flat manifold M, the…

Differential Geometry · Mathematics 2007-05-23 J. C. Loftin

The Schur's theorem of antiholomorphic type is proved for arbitrary almost Hermitian manifolds, namely: If a connected almost Hermitian manifold of dimension greater or equal to 6 is of pointwise constant antiholomorphic sectional…

Differential Geometry · Mathematics 2011-08-26 Ognian Kassabov

Let $\pi: \mathcal{X}^* \rightarrow B^*$ be an algebraic family of compact K\"ahler manifolds of complex dimension $n$ with negative first Chern class over a punctured disc $B^*\in \mathbb{C}$. Let $g_t$ be the unique K\"ahler-Einstein…

Differential Geometry · Mathematics 2017-06-07 Jian Song

In this article we study compact K\"ahler manifolds $X$ admitting non-singular holomorphic vector fields with the aim of extending to this setting the classical birational classification of projective varieties with tangent vector fields.…

Algebraic Geometry · Mathematics 2010-07-20 Jaume Amoros , Monica Manjarin , Marcel Nicolau

In this paper, we study MRC fibrations of compact K\"ahler manifolds with partially semi-positive curvature. We first prove that a compact K\"ahler manifold is rationally connected if its tangent bundle is BC-$p$ positive for all $1\leq…

Differential Geometry · Mathematics 2026-03-09 Shiyu Zhang , Xi Zhang

In Kaehler manifolds are investigated conformally flat totally real submanifolds, which are semiparallel or have semiparallel mean curvature vector.

Differential Geometry · Mathematics 2010-01-26 Ognian Kassabov

We show the theorem which provides some sufficient condition to the non-existence of a complete K\"ahler--Einstein metric of negative scalar curvature whose holomorphic sectional curvature is negatively pinched: Let $\Omega$ be a bounded…

Differential Geometry · Mathematics 2023-05-23 Gunhee Cho

In this note we study two features of submanifolds (subvarieties) with ample normal bundles in a compact K\"ahler manifold X. First, we study how algebraic X can be, i.e. we investigate the algebraic dimension. Second, we study curves with…

Algebraic Geometry · Mathematics 2011-06-23 Thomas Peternell

We prove that an admissible manifold (as defined by Apostolov, Calderbank, Gauduchon and T{\o}nnesen-Friedman), arising from a base with a local K\"ahler product of constant scalar curvature metrics, admits Generalized Quasi-Einstein…

Differential Geometry · Mathematics 2009-09-08 Gideon Maschler , Christina W. Tønnesen-Friedman

We study the J-invariant and J-anti-invariant cohomological subgroups of the de Rham cohomology of a compact manifold M endowed with an almost-K\"ahler structure (J, \omega, g). In particular, almost-K\"ahler manifolds satisfying a…

Differential Geometry · Mathematics 2014-10-28 Daniele Angella , Adriano Tomassini , Weiyi Zhang

One of the main purposes of this paper is to prove that on a complete K\"ahler manifold of dimension $m$, if the holomorphic bisectional curvature is bounded from below by -1 and the minimum spectrum $\lambda_1(M) \ge m^2$, then it must…

Differential Geometry · Mathematics 2007-05-23 Peter Li , Jiaping Wang

We prove some results on effective very ampleness and projective normality for some varieties with trivial canonical bundle. In the first part we prove an effective projective normality result for an ample line bundle on regular smooth…

Algebraic Geometry · Mathematics 2019-10-01 Jayan Mukherjee , Debaditya Raychaudhury

In this paper, we prove the Miyaoka-Yau inequality for compact K\"ahler manifolds with semi-positive canonical bundle. The key point of the proof is the estimate for the $L^2$-norm of the scalar curvature along the K\"ahler-Ricci flow.

Differential Geometry · Mathematics 2018-02-16 Ryosuke Nomura