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It is shown that a compact $n$-dimensional K\"ahler manifold with $\frac{n}{2}$-positive Calabi curvature operator has the rational cohomology of complex projective space. For even $n,$ this is sharp in the sense that the complex quadric…

Differential Geometry · Mathematics 2025-05-07 Kyle Broder , Jan Nienhaus , Peter Petersen , James Stanfield , Matthias Wink

We give an elementary proof of the following projectivity criterion of Huybrechts: a compact K\"ahler surface is projective if and only if the dual K\"ahler cone contains an inner integral point.

Algebraic Geometry · Mathematics 2007-05-23 Keiji Oguiso , Thomas Peternell

We show that in every dimension greater than or equal to 4, there exist compact Kaehler manifolds which do not have the homotopy type of projective complex manifolds. Thus they a fortiori are not deformation equivalent to a projective…

Algebraic Geometry · Mathematics 2015-08-14 Claire Voisin

Let $f\colon M^{2n}\to\mathbb{R}^{2n+p}$ denote an isometric immersion of a Kaehler manifold of complex dimension $n\geq 2$ into Euclidean space with codimension $p$. If $2p\leq 2n-1$, we show that generic rank conditions on the second…

Differential Geometry · Mathematics 2023-08-30 A. de Carvalho , S. Chion , M. Dajczer

We prove that a holomorphic line bundle on a projective manifold is pseudo-effective if and only if its degree on any member of a covering family of curves is non-negative. This is a consequence of a duality statement between the cone of…

Algebraic Geometry · Mathematics 2007-05-23 Sébastien Boucksom , Jean-Pierre Demailly , Mihai Paun , Thomas Peternell

We show that if $X$ is a projective hyperk\"ahler fourfold and there exists a nonzero effective divisor $D$ which is not of bi-elliptic type and contained in the boundary of the nef cone of $X$, then $X$ contains a rational curve. This is a…

Algebraic Geometry · Mathematics 2021-12-24 Haidong Liu

Minimal isometric immersions F in codimension two from a complete Kahler manifold into Euclidean space had been classified for dimension greater than or equal to 3. In this note we describe the non--minimal situation by showing that, if F…

Differential Geometry · Mathematics 2007-05-23 Luis A. Florit , Fangyang Zheng

In general, the product of harmonic forms is not harmonic. We study the top exterior power of harmonic two-forms on compact Kaehler manifolds. Often, it is not harmonic. This phenomenon is related to the geometry of the manifold and to the…

Algebraic Geometry · Mathematics 2007-05-23 D. Huybrechts

We describe properties of the K\"ahler cone of general Calabi-Yau-threefolds with Picard number $\rho(X)=2$ and prove the rationality of the K\"ahler cone, if $X$ is a Calabi-Yau-hypersurface in a ${\mathbb P}^2$-bundle over ${\mathbb P}^2$…

Algebraic Geometry · Mathematics 2007-05-23 Marco Kuehnel

We prove that a compact contact threefold which is bimeromorphically equivalent to a Kaehler manifold and not rationally connected is the projectivised tangent bundle of a Kaehler surface.

Algebraic Geometry · Mathematics 2010-05-11 Kristina Frantzen , Thomas Peternell

This paper consists of two main results. In the first one we describe all Kaehler immersions of a bounded symmetric domain into the infinite dimensional complex projective space in terms of the Wallach set of the domain. In the second one…

Differential Geometry · Mathematics 2012-04-16 Andrea Loi , Michela Zedda

In the first part of this note, we discuss the compact K\"ahler manifold with a strongly pseudo-effective tangent bundle. In the second part, we give new proof of the fact that the only projective manifolds with the big tangent bundle are…

Differential Geometry · Mathematics 2024-01-02 Xiaojun Wu

In this paper, we show that the \alpha_{m,2}-invariant of a smooth cubic surface with Eckardt points is strictly bigger than 2/3. This can be used to simplify Tian's original proof of the existence of Kaehler-Einstein metrics on such…

Algebraic Geometry · Mathematics 2009-11-12 Yalong Shi

For every compact K\"ahler manifold $X$ of algebraic dimension $a(X) = \dim X - 1$, we prove that $X$ has arbitrarily small deformations to some projective manifolds.

Algebraic Geometry · Mathematics 2020-12-16 Hsueh-Yung Lin

In this expository paper (Bourbaki talk) we survey results of Claire Voisin showing that there exist compact Kaehler manifolds which are not homeomorphic to any projective manifold.

Algebraic Geometry · Mathematics 2013-09-12 Daniel Huybrechts

Our goal is twofold. On one hand we show that the cones of divisors ample in codimension $k$ on a Mori dream space are rational polyhedral. On the other hand we study the duality between such cones and the cones of $k$-moving curves by…

Algebraic Geometry · Mathematics 2025-08-05 Maria Chiara Brambilla , Olivia Dumitrescu , Elisa Postinghel , Luis José Santana Sánchez

We construct a compact K\"ahler manifold of nonnegative quadratic bisectional curvature, which does not admit any K\"ahler metric of nonnegative orthogonal bisectional curvature. The manifold is a 7-dimensional K\"ahler C-space with second…

Differential Geometry · Mathematics 2011-10-11 Qun Li , Damin Wu , Fangyang Zheng

The K\"ahler cone of a compact manifold carries a natural Riemannian metric, given by the intersection product of its cohomology ring. We write down the curvature tensor of this metric by embedding the K\"ahler cone in the space of…

Algebraic Geometry · Mathematics 2012-11-30 Gunnar Þór Magnússon

Motivated by the classical statements of Mirror Symmetry, we study certain Kahler metrics on the complexified Kahler cone of a Calabi-Yau threefold, conjecturally corresponding to approximations to the Weil-Petersson metric near large…

Algebraic Geometry · Mathematics 2010-07-20 Thomas Trenner , P. M. H. Wilson

In this note we begin a systematic study of compact conformal manifolds of SCFTs in four dimensions (our notion of compactness is with respect to the topology induced by the Zamolodchikov metric). Supersymmetry guarantees that such…

High Energy Physics - Theory · Physics 2015-06-23 Matthew Buican , Takahiro Nishinaka