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Let M be a connected generic real-analytic CR-submanifold of a finite-dimensional complex vector space E. Suppose that for every point a in M the Lie algebra hol(M,a) of germs of all infinitesimal real-analytic CR-automorphisms of M at a is…

Complex Variables · Mathematics 2009-06-18 A. Isaev. , W. Kaup

An absolute parallelism for $2$-nondegenerate CR manifolds $M$ of hypersurface type was recently constructed independently by Isaev-Zaitsev, Medori-Spiro, and Pocchiola in the minimal possible dimension ($\dim M=5$), and for $\dim M=7$ in…

Differential Geometry · Mathematics 2021-02-23 Curtis Porter , Igor Zelenko

We show that a real K\"ahler submanifold in codimension $6$ is essentially a holomorphic submanifold of another real K\"ahler submanifold in lower codimension if the second fundamental form is not sufficiently degenerated. We also give a…

Differential Geometry · Mathematics 2019-05-15 Alcides de Carvalho , Felippe Guimarães

A locally conformally Kaehler (LCK) manifold is a complex manifold admitting a Kaehler covering M, with monodromy acting on M by Kaehler homotheties. A compact LCK manifold is Vaisman if it admits a holomorphic flow acting by non-trivial…

Algebraic Geometry · Mathematics 2007-05-23 L. Ornea , M. Verbitsky

Concerning the problem of classifying complete submanifolds of Euclidean space with codimension two admitting genuine isometric deformations, until now the only known examples with the maximal possible rank four are the real Kaehler minimal…

Differential Geometry · Mathematics 2018-08-22 M. Dajczer , Th. Vlachos

In this work we study the existence of invariant almost complex structures on real flag manifolds associated to split real forms of complex simple Lie algebras. We show that, contrary to the complex case where the invariant almost complex…

Differential Geometry · Mathematics 2017-08-04 Ana P. C. Freitas , Viviana del Barco , Luiz A. B. San Martin

E. Cartan's method of moving frames is applied to 3-dimensional manifolds $M$ which are CR-embedded in 5-dimensional real hyperquadrics $Q$ in order to classify $M$ up to CR symmetries of $Q$ given by the action of one of the Lie groups…

Differential Geometry · Mathematics 2021-02-23 Curtis Porter

We show that every point in a uniformly $2$-nondegenerate CR hypersurface is canonically associated with a model $2$-nondegenerate structure. The $2$-nondegenerate models are basic CR invariants playing the same fundamental role as quadrics…

Complex Variables · Mathematics 2024-04-11 Jan Gregorovič , Martin Kolář , David Sykes

The property of admitting an astheno-K\"ahler metric is not stable under the action of small deformations of the complex structure of a compact complex manifold. In this paper, we prove necessary cohomological conditions for the existence…

Differential Geometry · Mathematics 2023-05-08 Tommaso Sferruzza

In this paper we provide a positive answer to a conjecture due to A. J. Di Scala, A. Loi, H. Hishi (see [3, Conjecture 1]) claiming that a simply-connected homogeneous K\"ahler manifold M endowed with an integral K\"ahler form $\mu\omega$,…

Differential Geometry · Mathematics 2016-06-30 Andrea Loi , Roberto Mossa

In this article, we study minimal isometric immersions of K\"ahler manifolds into product of two real space forms. We analyse the obstruction conditions to the existence of pluriharmonic isometric immersions of a K\"ahler manifold into…

Differential Geometry · Mathematics 2021-08-10 Alcides de Carvalho , Iury Domingos

It is known that supersymmetric nonlinear sigma models for the compact Kahler manifolds G/H cannot be consistently coupled to supergravity, since the Kahler potentials are not invariant under the G transformation. We show that the…

High Energy Physics - Theory · Physics 2011-02-03 Taichiro Kugo , Tsutomu T. Yanagida

We study CR hypersurfaces in $\mathbb{C}^4$ that are Levi degenerate with constant rank Levi form, and moreover finitely nondegenerate. Each of these can be described as a deformation of a model CR hypersurface by adding terms of higher…

Complex Variables · Mathematics 2025-04-08 Jan Gregorovič , David Sykes

B. Y. Chen established sharp inequalities between certain Riemannian invariants and the squared mean curvature for submanifolds in real space form as well as in complex space form. In this paper we generalize Chen inequalities for…

Differential Geometry · Mathematics 2016-04-27 Mehraj Ahmad Lone , Mohammad Jamali , Mohammad Hasan Shahid

For any k which is at least 2, we exhibit complete k-curvature homogeneous neutral signature pseudo-Riemannian manifolds which are not k+1-affine curvature homogeneous, and hence not locally homogeneous. All the local scalar Weyl invariants…

Differential Geometry · Mathematics 2007-05-23 P. Gilkey , S. Nikcevic

We obtain an embedding theorem for compact strongly pseudoconvex CR manifolds which are bounadries of some complete Hermitian manifolds. We use this to compactify some negatively curved Kaehler manifolds with compact strongly pseudoconvex…

Complex Variables · Mathematics 2015-09-10 G. Marinescu , N. Yeganefar

In this paper, authors have established Chen's inequalities for the submanifolds of quaternionic Kaehler manifolds characterized by Ricci quarter-symmetric metric connection. Other than these inequalities, we have also derived generalized…

Differential Geometry · Mathematics 2021-05-10 Umair Ali Wani , Mehraj Ahmad Lone

Let $(M^n, g)$ be a compact K\"ahler manifold with nonpositive bisectional curvature. We show that a finite cover is biholomorphic and isometric to a flat torus bundle over a compact K\"ahler manifold $N^k$ with $c_1 < 0$. This confirms a…

Differential Geometry · Mathematics 2014-04-30 Gang Liu

We characterize compact locally conformally K\"ahler (l.c.K.) manifolds under the assumption of a purely conformal, holomorphic circle action. As an application, we determine the structure of the compact l.c.K. manifolds with parallel Lee…

Differential Geometry · Mathematics 2007-05-23 Yoshinobu Kamishima , Liviu Ornea

We prove that a product complex manifold cannot admit a complete K\"ahler metric with sectional curvature $K<c<0$ and Ricci curvature $Ric > d$, where $c$ and $d$ are constants. In particular, a product domain in $\C$ cannot cover a compact…

Differential Geometry · Mathematics 2007-05-23 Harish Seshadri