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We construct Einstein metrics of non-positive scalar curvature on certain solid torus bundles over a Fano Kahler-Einstein manifold. We show, among other things, that the negative Einstein metrics are conformally compact, and the Ricci-flat…

Differential Geometry · Mathematics 2011-03-07 Dezhong Chen

On $4$-symmetric symplectic spaces, invariant almost complex structures -- up to sign -- arise in pairs. We exhibit some $4$-symmetric symplectic spaces, with a pair of "natural" compatible (usually not positive) invariant almost complex…

Differential Geometry · Mathematics 2022-06-14 Michel Cahen , Simone Gutt , Manar Hayyani , Mohammed Raouyane

In this paper, we present some new properties for p-biharmonic hypersurfaces in Riemannian manifold. We also characterize the p-biharmonic submanifolds in an Einstein space. We construct a new example of proper p-biharmonic hypersurfaces.…

Differential Geometry · Mathematics 2021-11-24 Khadidja Mouffoki , Ahmed Mohammed Cherif

We show that a negative Einstein manifold admitting a proper isometric action of a connected unimodular Lie group with compact, possibly singular, orbit space splits isometrically as a product of a symmetric space and a compact negative…

Differential Geometry · Mathematics 2023-07-26 Christoph Böhm , Ramiro A. Lafuente

We prove that a closed oriented Einstein four-manifold is either anti-self-dual or (after passing to a double Riemann cover if necessary) K\"ahler-Einstein, provided that $\lambda_2 \geq -\frac{S}{12}$, where $\lambda_2$ is the middle…

Differential Geometry · Mathematics 2022-06-13 Xiaolong Li , Yongjia Zhang

Using the theory of totally real number fields we construct a new class of compact complex non-K{\"a}hler manifolds in every even complex dimension and study their analytic and geometric properties.

Algebraic Geometry · Mathematics 2022-08-30 Christian Miebach , Karl Oeljeklaus

We obtain restrictions on the rational homotopy types of mapping spaces and of classifying spaces of homotopy automorphisms by means of the theory of positive weight decompositions. The theory applies, in particular, to connected components…

Algebraic Topology · Mathematics 2023-08-25 Joana Cirici , Bashar Saleh

We study locally conformal calibrated $G_2$-structures whose underlying Riemannian metric is Einstein, showing that in the compact case the scalar curvature cannot be positive. As a consequence, a compact homogeneous $7$-manifold cannot…

Differential Geometry · Mathematics 2020-08-11 Anna Fino , Alberto Raffero

In this thesis, we study cohomological properties of non-K\"ahler manifolds. In particular, we are concerned in investigating the cohomology of compact (almost-)complex manifolds, and of manifolds endowed with special structures, e.g.,…

Differential Geometry · Mathematics 2013-02-05 Daniele Angella

We introduce the notion of a special monopole class on a four-manifold. This is used to prove restrictions on the smooth structures of Einstein manifolds. As an application we prove that there are Einstein four-manifolds which are simply…

Differential Geometry · Mathematics 2007-05-23 D. Kotschick

We study Einstein metrics on smooth compact 4-manifolds with an edge-cone singularity of specified cone angle along an embedded 2-manifold. To do so, we first derive modified versions of the Gauss-Bonnet and signature theorems for arbitrary…

Differential Geometry · Mathematics 2017-05-17 Michael Atiyah , Claude LeBrun

We classify Einstein metrics on $\mathbb{R}^4$ invariant under a four-dimensional group of isometries including a principal action of the Heisenberg group. The metrics are either Ricci-flat or of negative Ricci curvature. We show that all…

Differential Geometry · Mathematics 2021-07-12 Vicente Cortés , Arpan Saha

In this note, we give explicit examples of compact complex 3-folds which admit automorphisms that are isotopic to the identity through C $\infty$-diffeomorphisms but not through biholomorphisms. These automorphisms play an important role in…

Complex Variables · Mathematics 2017-04-12 Laurent Meersseman

In this expository paper we review on the existence problem of Einstein-Maxwell K\"ahler metrics, and make several remarks. Firstly, we consider a slightly more general set-up than Einstein-Maxwell K\"ahler metrics, and give extensions of…

Differential Geometry · Mathematics 2018-03-20 Akito Futaki , Hajime Ono

We show that every K-contact Einstein manifold is Sasakian-Einstein and discuss several corollaries of this result.

Differential Geometry · Mathematics 2007-05-23 Charles P. Boyer , Krzysztof Galicki

We study invariant pseudo-K\"ahler structures on a solvmanifold $G$ such that the Lie algebra $\mathfrak{g}$ is almost abelian, that is $\mathfrak{g}=\mathfrak{h}\rtimes\mathbb{R}$, with $\mathfrak{h}$ abelian; comparing with the…

Differential Geometry · Mathematics 2025-06-30 Diego Conti , Alejandro Gil-García

In this article we show how to calculate the group of automorphisms of flat K\"ahler manifolds. Moreover we are interested in the problem of classification of such manifolds up to biholomorphism. We consider these problems from two points…

Complex Variables · Mathematics 2022-10-06 Marek Hałenda , Rafał Lutowski

The holonomy algebras of Einstein not Ricci-flat pseudo-Riemannian manifolds of arbitrary signature are classified. As illustrating examples, the cases of Lorentzian manifolds, pseudo-Riemannian manifolds of signature $(2,n)$ and the…

Differential Geometry · Mathematics 2021-05-14 Anton S. Galaev

We present an explicit upper bound on the number of isolated homogeneous Einstein metrics on compact homogeneous spaces whose isotropy representations consist of pairwise inequivalent irreducibles. This is the BKK bound of the corresponding…

Differential Geometry · Mathematics 2025-09-15 Renato G. Bettiol , Hannah Friedman

It is well-known that every 6-dimensional strictly nearly K\"{a}hler manifold $(M,g,J)$ is Einstein with positive scalar curvature $scal>0$. Moreover, one can show that the space $E$ of co-closed primitive (1,1)-forms on $M$ is stable under…

Differential Geometry · Mathematics 2011-02-22 Andrei Moroianu , Uwe Semmelmann