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We obtain a class of Kaehler Einstein structures on the nonzero cotangent bundle of a Riemannian manifold of positive constant sectional curvature. The obtained class of Kaehler Einstein structure depends on one essential parameter, cannot…

Differential Geometry · Mathematics 2007-05-23 Dumitru Daniel Porosniuc

Our aim here is to investigate the holomorphic geometric structures on compact complex manifolds which may not be K\"ahler. We prove that holomorphic geometric structures of affine type on compact Calabi-Yau manifolds with polystable…

Differential Geometry · Mathematics 2016-02-16 Indranil Biswas , Sorin Dumitrescu

We introduce a new technique to the study and identification of submanifolds of simply-connected symmetric spaces of compact type based upon an approach computing $k$-positive Ricci curvature of the ambient manifolds and using this…

Differential Geometry · Mathematics 2022-05-20 Manuel Amann , Peter Quast , Masoumeh Zarei

We show that if a compact Kahler manifold X admits a cohomologically hyperbolic surjective endomorphism then its Kodaira dimension is non-positive. This gives an affirmative answer to a conjecture of Guedj in the holomorphic case. The main…

Dynamical Systems · Mathematics 2018-09-24 De-Qi Zhang

The aim of this thesis is to construct new examples of compact orbifolds $\mathcal{O}^4(\Theta)$ which admit a self dual Einstein (SDE) metric of positive scalar curvature $s>0$, with a one-dimensional group of isometries. In particular we…

Differential Geometry · Mathematics 2007-05-23 Luca Bisconti

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

The aim of this paper is to study Seifert bundle structures on simply connected 5--manifolds. We classify all such 5--manifolds which admit a Seifert bundle structure, and in a few cases all Seifert bundle structures are also classified.…

Differential Geometry · Mathematics 2007-05-23 János Kollár

Based on the work of Adams and Stuck as well as on the work of Zeghib, we classify the Lie groups which can act isometrically and locally effectively on Lorentzian manifolds of finite volume. In the case that the corresponding Lie algebra…

Differential Geometry · Mathematics 2013-05-31 Felix Günther

The classification of all possible holonomy algebras of Einstein and vacuum Einstein Lorentzian manifolds is obtained. It is shown that each such algebra appears as the holonomy algebra of an Einstein (resp., vacuum Einstein) Lorentzian…

Differential Geometry · Mathematics 2010-04-14 Anton S. Galaev

The goal of this paper is to illustrate different approaches to understand Euler characteristics in the setting of totally real commutative and non-commutative Iwasawa theory. In addition to this, and in the spirit of Hesselholt and…

Number Theory · Mathematics 2022-06-30 Guillem Sala Fernandez

We discuss how metric limits and rescalings of K\"ahler-Einstein metrics connect with Algebraic Geometry, mostly in relation to the study of moduli spaces of varieties, and singularities. Along the way, we describe some elementary examples,…

Differential Geometry · Mathematics 2025-09-16 Cristiano Spotti

It is known that the moduli space of Einstein structures in four dimensions is generally considered to be rigid so that Einstein metrics tend to be isolated modulo diffeomorphisms under infinitesimal Einstein deformations. We examine the…

Differential Geometry · Mathematics 2025-08-12 Jeongwon Ho , Kyung Kiu Kim , Hyun Seok Yang

We prove the instability of conformally K\"ahler, compact or ALF Einstein 4-manifolds with nonnegative scalar curvature which are not half conformally flat. This applies to all the known examples of gravitational instantons which are not…

Differential Geometry · Mathematics 2025-02-11 Olivier Biquard , Tristan Ozuch

This article presents a new and more elementary proof of the main Seiberg-Witten-based obstruction to the existence of Einstein metrics on smooth compact 4-manifolds. It also introduces a new smooth manifold invariant which conveniently…

Differential Geometry · Mathematics 2007-05-23 Claude LeBrun

We consider real isotropic geodesics on manifolds endowed with a pseudoconformal structure and their applications to the theory of lightlike hypersurfaces on such manifolds, the geometry of four-dimensional conformal structures of…

Differential Geometry · Mathematics 2007-05-23 Maks A. Akivis , Vladislav V. Goldberg

In this paper, we establish a priori estimates and existence results for solutions of a general class of fully non-linear equations on noncompact K\"{a}hler and Hermitian manifolds. As geometric applications, we construct complete…

Differential Geometry · Mathematics 2025-12-24 Hanzhang Yin

Two distinct non-singular interior models that describe anisotropic spherical configurations are presented in this work. We develop the Einstein field equations and the associated mass function in accordance with a static spherical…

General Relativity and Quantum Cosmology · Physics 2025-10-10 M. Sharif , Tayyab Naseer , Hira Shadab

The purpose of this article is to highlight the fascinating, but only very incompletely understood relation between Einstein's theory and its generalizations on the one hand, and the theory of indefinite, and in particular hyperbolic, Kac…

General Relativity and Quantum Cosmology · Physics 2007-05-23 H. Nicolai

The classification of Riemannian manifolds by the holonomy group of their Levi-Civita connection picks out many interesting classes of structures, several of which are solutions to the Einstein equations. The classification has two parts.…

Differential Geometry · Mathematics 2007-05-23 Richard Cleyton , Andrew Swann

Let $(M,J)$ be a complex manifold of complex dimension $n$. A $p$-K\"ahler structure on $(M,J)$ is a real, closed $(p,p)$-transverse form. In this paper, we address the conjecture of L. Alessandrini and G. Bassanelli on $(n-2)$-K\"ahler…

Differential Geometry · Mathematics 2025-06-17 Ettore Lo Giudice