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It is proved, that if a quasi-K\"ahler manifold $M$ of dimension greater or equal to 6 is of pointwise constant antiholomorphic sectional curvature $\nu$, then $\nu$, the scalar curvature and the $*$-scalar curvature of $M$ are constants.

微分几何 · 数学 2010-09-15 Georgi Ganchev , Ognian Kassabov

The Schur's theorem of antiholomorphic type is proved for arbitrary almost Hermitian manifolds, namely: If a connected almost Hermitian manifold of dimension greater or equal to 6 is of pointwise constant antiholomorphic sectional…

微分几何 · 数学 2011-08-26 Ognian Kassabov

In dimension greater than four, we prove that if a Hermitian non-Kaehler manifold is of pointwise constant antiholomorphic sectional curvatures, then it is of constant sectional curvatures.

微分几何 · 数学 2007-07-23 Georgi Ganchev , Ognian Kassabov

We prove the following results: An almost Hermitian manifold of indefinite metric is of pointwise constant holomorphic sectional curvature if the holomorphic sectional curvature is bounded from above and from below. If the antiholomorphic…

微分几何 · 数学 2010-08-12 Adrijan Borisov , Ognian Kassabov

We studied the axiom of anti-invariant 2-spheres and the axiom of co-holomorphic $(2n+1)$-spheres. We proved that a nearly K\"{a}hlerian manifold satisfying the axiom of anti-invariant 2-spheres is a space of constant holomorphic sectional…

微分几何 · 数学 2014-05-27 Hakan Mete Taştan

It is proved that if an AK2-manifold of dimension greater or equal to 6 is of pointwise constant antiholomorphic sectional curvature, then it is a 6-dimensional manifold of constant negative sectional curvature or a K\"ahler manifold of…

微分几何 · 数学 2010-09-15 Ognian Kassabov

A long-standing conjecture in complex geometry says that a compact Hermitian manifold with constant holomorphic sectional curvature must be K\"ahler when the constant is non-zero and must be Chern flat when the constant is zero. The…

微分几何 · 数学 2023-02-24 Peipei Rao , Fangyang Zheng

We show that a closed almost K\"ahler 4-manifold of globally constant holomorphic sectional curvature $k\geq 0$ with respect to the canonical Hermitian connection is automatically K\"ahler. The same result holds for $k<0$ if we require in…

微分几何 · 数学 2017-09-18 Mehdi Lejmi , Markus Upmeier

The following theorem is proved: If an AH3-manifold M of dimension greather or equal to 6 is of pointwise constant antiholomorphic sectional curvature, then M is a real space form or a complex space form.

微分几何 · 数学 2010-09-16 Ognian Kassabov

A classification theorem for nearly K\"ahler manifolds of constant antiholomorphic sectional curvature is proved.

微分几何 · 数学 2010-09-15 Georgi Ganchev , Ognian Kassabov

It is proved that if an almost K\"ahler manifold of dimension greater or equal to 8 is of pointwise constant antiholomorphic sectional curvature, then it is a complex space form.

微分几何 · 数学 2010-10-08 Maria Falcitelli , Angela Farinola , Ognian Kassabov

It is known, that if a 2m-dimensional Kahler manifold satisfies the axiom of holomorphic 2n-spheres (1<n<m) or the axiom of antiholomorphic n-spheres (2<n), it is of constant holomorphic sectional curvature. In this paper the same result is…

微分几何 · 数学 2010-04-26 Ognian Kassabov

In this article, we propose the following conjecture: if the Strominger connection of a compact Hermitian manifold has constant non-zero holomorphic sectional curvature, then the Hermitian metric must be K\"ahler. The main result of this…

微分几何 · 数学 2023-02-24 Shuwen Chen , Fangyang Zheng

Criterions for constancy of the holomorphic sectional curvature and the antiholomorphic sectional curvature are proved for almost Hermitian manifolds. It is shown, that an almost Hermitian manifold satisfying the axiom of antiholomorphic…

微分几何 · 数学 2010-04-22 Ognian Kassabov

A well known conjecture in complex geometry states that a compact Hermitian manifold with constant holomorphic sectional curvature must be K\"ahler if the constant is non-zero and must be Chern flat if the constant is zero. The conjecture…

微分几何 · 数学 2022-07-18 Yulu Li , Fangyang Zheng

A long-standing conjecture in non-K\"ahler geometry states that if the Chern (or Levi-Civita) holomorphic sectional curvature of a compact Hermitian manifold is a constant $c$, then the metric must be K\"ahler when $c\neq 0$ and must be…

微分几何 · 数学 2026-03-17 Yulu Li , Fangyang Zheng

In this note we prove the following result: There is a positive constant $\epsilon(n,\Lambda)$ such that if $M^n$ is a simply connected compact K$\ddot{a}$hler manifold with sectional curvature bounded from above by $\Lambda$, diameter…

微分几何 · 数学 2008-11-10 Hong Huang

We give a condition for an almost constant-type manifold to be a constant-type manifold, and holomorphic and $R$-invariant submanifolds of almost Hermitian manifolds are studied. Generalizations of some results in [5] are given.

微分几何 · 数学 2013-11-12 Hakan Mete Taştan

In this paper, we study a general almost Schur Lemma on pseudo-Hermitian (2n+1)-manifolds $(M,J,\theta)$ for $n\geq2$. When the equality of almost Schur inequality holds, we derive the contact form $\theta$ is pseudo-Einstein and the…

微分几何 · 数学 2014-05-14 Jui-Tang Chen , Nguyen Thac Dung , Chin-Tung Wu

An old open question in non-K\"ahler geometry predicts that any compact Hermitian manifold with constant holomorphic sectional curvature must be K\"ahler or Chern flat. The conjecture is known to be true in dimension $2$ due to the work by…

微分几何 · 数学 2025-06-19 Xin Huang , Fangyang Zheng
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