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A complex flag manifold F= G /Q decomposes into finitely many real orbits under the action of a real form of G. Their embedding into F define on them CR manifold structures. We characterize the closed real orbits which are finitely…

Differential Geometry · Mathematics 2023-01-02 Stefano Marini , Costantino Medori , Mauro Nacinovich

In this paper, we study the CR submanifolds of maximal CR dimension with flat normal connection of a complex projective space. We first investigate the position of the umbilical normal vector in the normal bundle, especially for the…

Differential Geometry · Mathematics 2015-12-29 Liang Zhang , Man Su , Pan Zhang

We introduce a new class of lightlike submanifolds, namely, Screen Transversal Cauchy Riemann (STCR)-lightlike submanifolds, of indefinite Kaehler manifolds. We show that this new class is an umbrella of screen transversal lightlike, screen…

Differential Geometry · Mathematics 2018-11-11 Burçin Doğan , Bayram Şahin , Erol Yaşar

In this paper, we study a special type of compact Hermitian manifolds that are Strominger K\"ahler-like, or SKL for short. This condition means that the Strominger connection (also known as Bismut connection) is K\"ahler-like, in the sense…

Differential Geometry · Mathematics 2023-03-31 Shing-Tung Yau , Quanting Zhao , Fangyang Zheng

We study nonlinear automorphisms of Levi degenerate hypersurfaces of finite multitype. By recent results of Kolar, Meylan and Zaitsev, the Lie algebra of infinitesimal CR automorphisms may contain a graded component consisting of nonlinear…

Complex Variables · Mathematics 2015-08-11 Martin Kolar , Francine Meylan

We consider $F: M \to N$ a minimal oriented compact real 2n-submanifold M, immersed into a Kaehler-Einstein manifold N of complex dimension 2n, and scalar curvature R. We assume that $n \geq 2$ and F has equal Kaehler angles. Our main…

Differential Geometry · Mathematics 2007-05-23 Isabel M. C. Salavessa , Giorgio Valli

It is shown that two Levi-Tanaka and infinitesimal CR automorphism algebras, associated with a totally nondegenerate model of CR dimension one are isomorphic. As a result, the model surfaces are maximally homogeneous and standard. This…

Differential Geometry · Mathematics 2016-10-28 Masoud Sabzevari

We give four constructions of non-$\partial\bar\partial$ (hence non-K\"ahler) manifolds: (1) A simply connected page-$1$-$\partial\bar\partial$-manifold (2) A simply connected $dd^c+3$-manifold (3) For any $r\geq 2$, a simply connected…

Algebraic Geometry · Mathematics 2023-06-27 Hisashi Kasuya , Jonas Stelzig

Let $M_1$ and $M_2$ be two K\"ahler manifolds. One says that $M_1$ and $M_2$ are "relatives" if they share a non-trivial K\"ahler submanifold $S$, namely, if there exist two holomorphic and isometric immersions (K\"ahler immersions) $h_1: S…

Differential Geometry · Mathematics 2013-08-07 Roberto Mossa

We consider compact $CR$ manifolds of arbitrary $CR$ codimension that satisfy certain geometric conditions in terms of their Levi form. Over these compact $CR$ manifolds, we construct a deformation of the trivial $CR$ line bundle over $M$…

Complex Variables · Mathematics 2019-05-29 Judith Brinkschulte , C. Denson Hill

n this paper, we obtain a geometric inequality between the length of the second fundamental form and the length of Lee form in terms of the warping function for a CR-warped product submanifold in a locally conformal Kaehler space form. The…

Differential Geometry · Mathematics 2020-04-01 Siraj Uddin , Khushwant Singh , Fatimah Alghamdi , Cengizhan Murathan

Searching normal forms for real analytic submanifolds of C^n involves convergence problems. In 1983, J.K. Moser and S.M. Webster provided examples of real analytic surfaces in C^2 having an isolated hyperbolic (in the sense of E. Bishop)…

Complex Variables · Mathematics 2007-05-23 Joël Merker

In this note, we consider submanifolds of a generalized K\"ahler manifold that are CR-submanifolds for the two associated Hermitian structures. Then, we establish the conditions for the induced, generalized F structure to be a CRFK…

Differential Geometry · Mathematics 2017-08-07 Izu Vaisman

Motivated by the geometry of Levi degenerate CR hypersurfaces, we define a pre-K\"ahler structure on a complex manifold as a pre-symplectic structure compatible with the almost complex structure, i.e. a closed (1,1)-form. Extending Freeman…

Differential Geometry · Mathematics 2025-05-16 Omid Makhmali , David Sykes

We study the rigidity of holomorphic mappings from a neighborhood of a Levi-nondegenerate CR hypersurface $M$ with signature $l$ into a hyperquadric $Q_{l'}^{N} \subseteq \mathbb{CP}^{N+1}$ of larger dimension and signature. We show that if…

Complex Variables · Mathematics 2010-11-05 Peter Ebenfelt , Ravi Shroff

We study non-degenerate CR geometries of hypersurface type that are symmetric in the sense that, at each point, there is a CR transformation reversing the CR distribution at that point. We show that such geometries are either flat or…

Complex Variables · Mathematics 2018-08-10 Jan Gregorovič , Lenka Zalabová

We improve results of Baouendi, Rothschild and Treves and of Hill and Nacinovich by finding a much weaker sufficient condition for a CR manifold of type $(n,k)$ to admit a local CR embedding into a CR manifold of type $(n+\ell,k-\ell)$.…

Complex Variables · Mathematics 2022-04-05 M. G. Cowling , M. Ganji , A. Ottazzi , G. Schmalz

Let $X$ be an orientable compact Levi-flat CR manifold and let $L$ be a positive CR complex line bundle over $X$. We prove that certain microlocal conjugations of the associated Szeg\H{o} kernel admits an asymptotic expansion with respect…

Complex Variables · Mathematics 2018-04-03 Chin-Yu Hsiao , George Marinescu

A locally conformally K\"ahler (LCK) manifold is a complex manifold covered by a K\"ahler manifold, with the covering group acting by homotheties. We show that if such a compact manifold X admits a holomorphic submersion with positive…

Differential Geometry · Mathematics 2020-07-30 Liviu Ornea , Maurizio Parton , Victor Vuletescu

In this paper we study 3-submersions from a QR-hypersurface of a quaternionic Kaehler manifold onto an almost quaternionic hermitian manifold. We also prove the non-existence of quaternionic submersions between quaternionic Kaehler…

Differential Geometry · Mathematics 2011-06-14 Gabriel Eduard Vilcu