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We study various classes of real hypersurfaces that are not embeddable into more special hypersurfaces in higher dimension, such as spheres, real algebraic compact strongly pseudoconvex hypersurfaces or compact pseudoconvex hypersurfaces of…

Complex Variables · Mathematics 2015-02-16 Xiaojun Huang , Dmitri Zaitsev

We prove that there are no pseudoholomorphic theories of anything other than curves, even if one allows more general spaces than almost complex manifolds. The proof is elementary, except for theories of pseudoholomorphic hypersurfaces,…

Differential Geometry · Mathematics 2010-09-29 Benjamin McKay

We prove the non-existence of real analytic Levi flat hypersurface whose complement is 1-convex and Levi foliation is transversely affine in compact Kahler surfaces.

Complex Variables · Mathematics 2022-09-20 Masanori Adachi , Severine Biard

In this article, we give a counterexample to the Lefschetz hyperplane theorem for non-singular quasi-projective varieties. A classical result of Hamm-L\^{e} shows that Lefschetz hyperplane theorem can hold for hyperplanes in general…

Algebraic Geometry · Mathematics 2023-01-13 Ananyo Dan

Conformal fundamental forms populate a minimal generating set for low differential order invariants of conformal hypersurface embeddings. In this work we complete the characterization of conformal fundamental forms by proving the general…

Differential Geometry · Mathematics 2025-09-26 Samuel Blitz

We construct examples of inhomogeneous isoparametric real hypersurfaces in complex hyperbolic spaces.

Differential Geometry · Mathematics 2010-11-24 J. Carlos Diaz-Ramos , Miguel Dominguez-Vazquez

We classify real hypersurfaces in complex space forms with constant principal curvatures and whose Hopf vector field has two nontrivial projections onto the principal curvature spaces. In complex projective spaces such real hypersurfaces do…

Differential Geometry · Mathematics 2009-11-19 Jose Carlos Diaz-Ramos , Miguel Dominguez-Vazquez

The classification of isoparametric hypersurfaces in spheres with four or six different principal curvatures is still not complete. In this paper we develop a structural approach that may be helpful for a classification. Instead of working…

Differential Geometry · Mathematics 2017-09-06 Anna Siffert

We describe extrinsic hyperspheres and totally geodesic hypersurfaces in manifolds with special holonomy. In particular we prove the nonexistence of extrinsic hyperspheres in quaternion-Kaehler manifolds. We develop a new approach to…

Differential Geometry · Mathematics 2019-01-08 Tillmann Jentsch , Andrei Moroianu , Uwe Semmelmann

In this paper we achieve a first concrete step towards a better understanding of the so-called Bernstein problem in higher dimensional Heisenberg groups. Indeed, in the sub-Riemannian Heisenberg group $\mathbb{H}^n$, with $n\geq 2$, we show…

Differential Geometry · Mathematics 2024-03-04 Andrea Pinamonti , Simone Verzellesi

This survey paper, aimed at nonexperts in the field, explores various proofs of nonexistence of real analytic Levi-flat hypersurfaces in $\mathbb CP^n$, $n>2$. Some generalizations and other related results are also discussed.

Complex Variables · Mathematics 2025-04-15 Rasul Shafikov

We prove a conjecture formulated by Pablo M. Chacon and Guillermo A. Lobos in [Pseudo-parallel Lagrangian submanifolds in complex space forms, Differential Geom. Appl.] stating that every Lagrangian pseudo-parallel submanifold of a complex…

Differential Geometry · Mathematics 2008-11-24 F. Dillen , J. Van der Veken , L. Vrancken

This is a revised version (minor changes and a deeper insight in the positive curvature case). We prove some Caccioppoli's inequalities for the traceless part of the second fundamental form of a complete, noncompact, finite index, constant…

Differential Geometry · Mathematics 2012-03-23 Said Ilias , Barbara Nelli , Marc Soret

In this paper we prove the following theorem. Main Theorem. Let n >= 3 and m >= 3n/2 +7. Then there exists no C^m Levi-flat real hypersurface M in P_n. The condition that M is Levi-flat means that when M is locally defined by the vanishing…

Complex Variables · Mathematics 2016-09-07 Yum-Tong Siu

We show that Bergman completeness is not a quasi-conformal invariant for general Riemann surfaces.

Complex Variables · Mathematics 2018-02-21 Xu Wang

We prove analogues of several well-known results concerning rational morphisms between quadrics for the class of so-called quasilinear $p$-hypersurfaces. These hypersurfaces are nowhere smooth over the base field, so many of the geometric…

Algebraic Geometry · Mathematics 2013-11-19 Stephen Scully

The existence of closed hypersurfaces of prescribed curvature in semi-riemannian manifolds is proved provided there are barriers.

Differential Geometry · Mathematics 2007-05-23 Claus Gerhardt

We prove that there is no class-dual for almost all sublinear models on graphs.

Machine Learning · Computer Science 2014-06-02 Brijnesh Jain

We classify the space-like biharmonic surfaces in 3-dimension pseudo-Riemannian space form, and construct explicit examples of proper biharmonic hypersurfaces in general ADS space.

Differential Geometry · Mathematics 2008-08-12 Wei Zhang

The space $SL(2,\mathbb{R})\times SL(2,\mathbb{R})$ admits a natural homogeneous pseudo-Riemannian nearly Kaehler structure. We investigate almost complex surfaces in this space. In particular we obtain a complete classification of the…

Differential Geometry · Mathematics 2020-06-23 Elsa Ghandour , Luc Vrancken