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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.

Differential Geometry · Mathematics 2010-09-15 Georgi Ganchev , Ognian Kassabov

Let M be an almost Hermitian manifold of dimension greater or equal to 6. The following theorems are proved: Theorem 1. If M is of pointwise constant {\theta}-holomorphic sectional curvature for a number {\theta} in (0,{\pi}/2) then M is of…

Differential Geometry · Mathematics 2010-09-15 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…

Differential Geometry · Mathematics 2010-08-12 Adrijan Borisov , 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.

Differential Geometry · Mathematics 2007-07-23 Georgi Ganchev , 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…

Differential Geometry · Mathematics 2014-05-27 Hakan Mete Taştan

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…

Differential Geometry · Mathematics 2017-09-18 Mehdi Lejmi , Markus Upmeier

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…

Differential Geometry · Mathematics 2023-02-24 Peipei Rao , Fangyang Zheng

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.

Differential Geometry · Mathematics 2010-10-08 Maria Falcitelli , Angela Farinola , Ognian Kassabov

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…

Differential Geometry · Mathematics 2010-09-15 Ognian Kassabov

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…

Differential Geometry · Mathematics 2010-04-22 Ognian Kassabov

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…

Differential Geometry · Mathematics 2014-05-14 Jui-Tang Chen , Nguyen Thac Dung , Chin-Tung Wu

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

Differential Geometry · Mathematics 2010-09-15 Georgi Ganchev , Ognian Kassabov

It is proved, that if an almost Hermitian manifold satisfies the axiom of coholomorphic spheres, it is conformal flat.

Differential Geometry · Mathematics 2010-04-23 Ognian Kassabov

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.

Differential Geometry · Mathematics 2010-09-16 Ognian Kassabov

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.

Differential Geometry · Mathematics 2013-11-12 Hakan Mete Taştan

In this paper, we study the existence of constant holomorphic d-scalar curvature and the prescribing holomorphic d-scalar curvature problem on closed, connected almost Hermitian manifolds of dimension $n\geq6$. In addition, we obtain an…

Differential Geometry · Mathematics 2023-02-27 Jianquan Ge , Yi Zhou

It is proved that if an almost Hermitian manifold of dimension greater than 4 has vanishing (classical) Bochner curvature tensor and is not Kaehlerian at a point, then it is flat in a neighbourhood of this point.

Differential Geometry · Mathematics 2011-08-31 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…

Differential Geometry · Mathematics 2022-07-18 Yulu Li , Fangyang Zheng

We prove some Liouville type results for generalized holomorphic maps in three classes: maps from pseudo-Hermitian manifolds to almost Hermitian manifolds, maps from almost Hermitian manifolds to pseudo-Hermitian manifolds and maps from…

Differential Geometry · Mathematics 2021-10-08 Haojie Chen , Yibin Ren

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…

Differential Geometry · Mathematics 2010-04-26 Ognian Kassabov
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