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In this paper, we establish compactness results of some class of conformally compact Einstein 4-manifolds. In the first part of the paper, we improve the earlier results obtained by Chang-Ge. In the second part of the paper, as…

Differential Geometry · Mathematics 2019-07-15 Sun-Yung A. Chang , Yuxin Ge , Jie Qing

We give a classification of toric anti-self-dual conformal structures on compact 4-orbifolds with positive Euler characteristic. Our proof is twistor theoretic: the interaction between the complex torus orbits in the twistor space and the…

Differential Geometry · Mathematics 2009-09-22 Dominic Wright

We provide an explicit resolution of the existence problem for extremal Kaehler metrics on toric 4-orbifolds M with second Betti number b2(M)=2. More precisely we show that M admits such a metric if and only if its rational Delzant polytope…

Differential Geometry · Mathematics 2016-11-28 Vestislav Apostolov , David M. J. Calderbank , Paul Gauduchon

The self-dual Einstein equations on a compact Riemannian 4-manifold can be expressed as a quadratic condition on the curvature of an $SU(2)$ (spin) connection which is a covariant generalization of the self-dual Yang-Mills equations. Local…

High Energy Physics - Theory · Physics 2007-05-23 C. G. Torre

We find a new obstruction for a real Einstein 4-orbifold with an A1-singularity to be a limit of smooth Einstein 4-manifolds. The obstruction is a curvature condition at the singular point. For asymptotically hyperbolic metrics, with…

Differential Geometry · Mathematics 2011-05-26 Olivier Biquard

We compute a Bochner type formula for static three-manifolds and deduce some applications in the case of positive scalar curvature. We also explain in details the known general construction of the (Riemannian) Einstein (n+1)-manifold…

Differential Geometry · Mathematics 2015-03-13 L. Ambrozio

We study 4-dimensional Poincar\'e-Einstein manifolds whose conformal class contains a K\"ahler metric. Such Einstein metrics are non-K\"ahler and admit a Killing field extending to the conformal infinity, and the Einstein equation reduces…

Differential Geometry · Mathematics 2025-10-07 Mingyang Li , Hongyi Liu

We give an explicit local classification of conformally equivalent but oppositely oriented Kaehler metrics on a 4-manifold which are toric with respect to a common 2-torus action. In the generic case, these structures have an intriguing…

Differential Geometry · Mathematics 2013-03-01 Vestislav Apostolov , David M. J. Calderbank , Paul Gauduchon

In the following work we investigate the structure of Einstein manifolds with positive scalar curvature whose curvature operator is sufficiently close to the identity operator in dimensions below 12. An Einstein manifold with positive…

Differential Geometry · Mathematics 2023-11-07 Kevin Poljsak

The twistor space of self-dual positive Einstein manifolds naturally admits two 1-parameter families of Riemannian metrics, one is the family of canonical deformation metrics and the other is the family introduced by B. Chow and D. Yang in…

Differential Geometry · Mathematics 2008-05-15 Ryoichi Kobayashi , Kensuke Onda

For Einstein manifolds with negative scalar curvature admitting an isometric action of a Lie group G with compact, smooth orbit space, we show the following rigidity result: The nilradical N of G acts polarly, and the N-orbits can be…

Differential Geometry · Mathematics 2023-01-11 Christoph Böhm , Ramiro A. Lafuente

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

Building on previous results, we complete the classification of compact oriented Einstein 4-manifolds with det (W^+) > 0. There are, up to diffeomorphism, exactly 15 manifolds that carry such metrics, and, on each of these manifolds, such…

Differential Geometry · Mathematics 2020-07-03 Claude LeBrun

We classify those curvature-homogeneous Einstein four-manifolds, of all metric signatures, which have a complex-diagonalizable curvature operator. They all turn out to be locally homogeneous. More precisely, any such manifold must be either…

Differential Geometry · Mathematics 2007-05-23 Andrzej Derdzinski

This paper considers the existence of conformally compact Einstein metrics on 4-manifolds. A reasonably complete understanding is obtained for the existence of such metrics with prescribed conformal infinity, when the conformal infinity is…

Differential Geometry · Mathematics 2008-03-18 Michael T. Anderson

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

We find new obstructions to the desingularization of compact Einstein orbifolds by smooth Einstein metrics. These new obstructions, specific to the compact situation, raise the question of whether a compact Einstein $4$-orbifold which is…

Differential Geometry · Mathematics 2021-10-26 Tristan Ozuch

Let $(M^n,g)$, $n \ge 4$, be a compact simply-connected Riemannian manifold with nonnegative isotropic curvature. Given $0<l\le L$, we prove that there exists $\eps = \eps (l,L,n)$ satisfying the following: If the scalar curvature $s$ of…

Differential Geometry · Mathematics 2009-04-07 Harish Seshadri

We present a local classification of conformally equivalent but oppositely oriented 4-dimensional Kaehler metrics which are toric with respect to a common 2-torus action. In the generic case, these "ambitoric" structures have an intriguing…

Differential Geometry · Mathematics 2016-11-28 Vestislav Apostolov , David M. J. Calderbank , Paul Gauduchon

The classification of homogeneous compact Einstein manifolds in dimension six is an open problem. We consider the remaining open case, namely left-invariant Einstein metrics $g$ on $G = \mathrm{SU}(2) \times \mathrm{SU}(2) = S^3 \times…

Differential Geometry · Mathematics 2018-07-10 Florin Belgun , Vicente Cortés , Alexander S. Haupt , David Lindemann