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We derive necessary conditions for a complex projective structure on a complex surface to arise via the Levi-Civita connection of a (pseudo-)K\"ahler metric. Furthermore we show that the (pseudo-)K\"ahler metrics defined on some domain in…

Differential Geometry · Mathematics 2023-07-19 Thomas Mettler

We give necessary and sufficient conditions for Riemannian maps to be biharmonic. We also define pseudo umbilical Riemannian maps as a generalization of pseudo-umbilical submanifolds and show that such Riemannian maps put some restrictions…

Differential Geometry · Mathematics 2010-12-10 Bayram Sahin

We consider four (real or complex) dimensional hyper-K\"ahler metrics with a conformal symmetry K. The three-dimensional space of orbits of K is shown to have an Einstein-Weyl structure which admits a shear-free geodesics congruence for…

Differential Geometry · Mathematics 2007-05-23 Maciej Dunajski , Paul Tod

An almost quaternion-Hermitian structure on a Riemannian manifold $(M^{4n},g)$ is a reduction of the structure group of $M$ to $\mathrm{Sp}(n)\mathrm{Sp}(1)\subset \mathrm{SO}(4n)$. In this paper we show that a compact simply connected…

Differential Geometry · Mathematics 2019-01-08 Andrei Moroianu , Mihaela Pilca , Uwe Semmelmann

We consider compatibility conditions between Poisson and Riemannian structures on smooth manifolds by means of a contravariant partially complex structure, or $f$-structure, introducing the notion of (almost) K\"ahler--Poisson manifolds. In…

Symplectic Geometry · Mathematics 2017-09-11 Nicolás Martínez Alba , Andrés Vargas

In this paper, we construct tools from the holomorphic twistor spaces that we introduced in \cite{Gindi1} to derive results about the complex geometries of their base manifolds. In particular, we develop a new approach to studying…

Differential Geometry · Mathematics 2018-11-22 Steven Gindi

A $p$-K\"ahler structure on a complex manifold of complex dimension $n$ is given by a $d$-closed transverse real $(p,p)$-form. In the paper we study the existence of $p$-K\"ahler structures on compact quotients of simply connected Lie…

Differential Geometry · Mathematics 2024-04-04 Anna Fino , Asia Mainenti

We introduce spin-harmonic structures, a class of geometric structures on Riemannian manifolds of low dimension which are defined by a harmonic unitary spinor. Such structures are related to SU(2) (dim=4,5), SU(3) (dim=6) and G_2 (dim=7)…

Differential Geometry · Mathematics 2022-01-17 Giovanni Bazzoni , Lucia Martin-Merchan , Vicente Munoz

We consider compact oriented four-manifolds with harmonic self-dual Weyl curvature in addition to a pinching condition.

Differential Geometry · Mathematics 2025-12-02 Inyoung Kim

We investigate the local structure of four-dimensional Lorentzian quasi-Einstein manifolds under conditions on the Weyl tensor. We show that if the Weyl tensor is harmonic and the potential function preserves this harmonicity then, in the…

Differential Geometry · Mathematics 2020-01-08 Miguel Brozos-Vázquez , Eduardo García-Río , Xabier Valle-Regueiro

We construct new complex-valued harmonic morphisms from Euclidean spaces from functions which are holomorphic with respect to Hermitian structures. In particular, we give the first global examples of complex-valued harmonic morphisms from…

dg-ga · Mathematics 2008-02-03 P. Baird , J. C. Wood

In this article, we study harmonic symmetries on the compact locally conformally K\"{a}hler manifold $M$ of $dim_{\mathbb{C}}=n$. The space of harmonic symmetries is a subspace of harmonic differential forms which defined by the kernel of a…

Differential Geometry · Mathematics 2022-02-01 Teng Huang

The existence of some complex geometrical structures on a compact manifold such as complex structures, Kaehler (pseudo-Kaehler) structures often impose certain restrictions on its underling topological or differentiable manifold. In this…

Complex Variables · Mathematics 2016-01-15 Keizo Hasegawa

We show that a compact oriented riemannian four-manifold with harmonic and pinched self-dual Weyl curvature is anti-self-dual if the type is nonpositive. The main part is to show that there is an almost-K\"ahler structure outside the zero…

Differential Geometry · Mathematics 2025-12-02 Inyoung Kim

We study complex non-K\"ahler manifolds with Hermitian metrics being locally conformal to metrics with special cohomological properties. In particular, we provide examples where the existence of locally conformal holomorphic-tamed…

Differential Geometry · Mathematics 2016-08-04 Daniele Angella , Luis Ugarte

A conformal product structure on a Riemannian manifold is a Weyl connection with reducible holonomy. We give the geometric description of all compact K\"ahler manifolds admitting conformal product structures

Differential Geometry · Mathematics 2024-05-15 Andrei Moroianu , Mihaela Pilca

Answering a conjecture by S. Kobayashi, in 1986, K. Sekigawa and L. Vanhecke proved that an almost hermitian manifold whose local geodesic symmetries preserve the K\"ahler 2-form is a locally symmetric hermitian space. In the present paper,…

Symplectic Geometry · Mathematics 2025-08-27 Pierre Bieliavsky , Maxime Willaert

Let $G/K$ be an irreducible Hermitian symmetric spaces of compact type with the standard homogeneous complex structure. Then the real symplectic manifold $(T^*(G/K),\Omega)$ has the natural complex structure $J^-$. We construct all…

Differential Geometry · Mathematics 2015-06-26 I. V. Mykytyuk

We call a quaternionic Kaehler manifold with non-zero scalar curvature, whose quaternionic structure is trivialized by a hypercomplex structure, a hyper-Hermitian quaternionic Kaehler manifold. We prove that every locally symmetric…

Differential Geometry · Mathematics 2007-05-23 Bogdan Alexandrov

We show that Weyl spaces provide a natural context for harmonic morphisms.

Differential Geometry · Mathematics 2007-05-23 E. Loubeau , R. Pantilie