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We show that compact Riemannian manifolds, regarded as metric spaces with their global geodesic distance, cannot contain a number of rigid structures such as (a) arbitrarily large regular simplices or (b) arbitrarily long sequences of…

Metric Geometry · Mathematics 2021-01-06 Alexandru Chirvasitu

We classify invariant almost complex structures on homogeneous manifolds of dimension 6 with semi-simple isotropy. Those with non-degenerate Nijenhuis tensor have the automorphism group of dimension either 14 or 9. An invariant almost…

Differential Geometry · Mathematics 2014-02-13 Dmitri V. Alekseevsky , Boris Kruglikov , Henrik Winther

Almost para-Hermitian manifold it is manifold equipped with almost para-complex structure and compatible pseudo-metric of neutral signature. It is considered a class of immersions of almost para-Hermitian manifolds into almost…

Differential Geometry · Mathematics 2017-10-27 Piotr Dacko

It is proved that any smooth manifold $\mathcal M$ of dimension $m$ admits a smooth polynomially convex embedding into $\mathbb C^n$ when $n\geq \lfloor 5m/4\rfloor$. Further, such embeddings are dense in the space of smooth maps from…

Complex Variables · Mathematics 2025-04-03 Purvi Gupta , Rasul Shafikov

We prove that each sub-Riemannian manifold can be embedded in some Euclidean space preserving the length of all the curves in the manifold. The result is an extension of Nash $C^1$ Embedding Theorem. For more general metric spaces the same…

Metric Geometry · Mathematics 2016-02-17 Enrico Le Donne

Almost-isometries are quasi-isometries with multiplicative constant one. Lifting a pair of metrics on a compact space gives quasi-isometric metrics on the universal cover. Under some additional hypotheses on the metrics, we show that there…

Group Theory · Mathematics 2016-07-19 Aditi Kar , Jean-Francois Lafont , Benjamin Schmidt

The celebrated Nash Embedding Theorem asserts that every closed Riemannian manifold can be isometrically embedded into a sufficiently high-dimensional Euclidean space. In this paper, we prove an analogous result in the conformally compact…

Differential Geometry · Mathematics 2025-12-09 Marco Usula

We study pseudoholomorphic discs with boundaries attached to a real hypersurface in an almost complex manifold. We give sufficient conditions for filling a one sided neighborhood of the hypersurface by the discs.

Complex Variables · Mathematics 2008-01-10 Alexandre Sukhov , Alexander Tumanov

We study the spaces of embeddings of manifolds in a Euclidean space. More precisely we look at the homotopy fiber of the inclusion of these spaces to the spaces of immersions. As a main result we express the rational homotopy type of…

Algebraic Topology · Mathematics 2021-03-25 Benoit Fresse , Victor Turchin , Thomas Willwacher

Almost hypercomplex pseudo-Hermitian manifolds are considered. Isotropic hyper-K\"ahler manifolds are introduced. A 4-parametric family of 4-dimensional manifolds of this type is constructed on a Lie group. This family is characterized…

Differential Geometry · Mathematics 2012-05-09 Kostadin Gribachev , Mancho Manev

We construct compact polyhedra with $m$-gonal faces whose links are generalized 3-gons. It gives examples of cocompact hyperbolic bildings of type $P(m,3)$. For $m=3$ we get compact spaces covered by Euclidean buildings of type $A_2$.

Combinatorics · Mathematics 2007-05-23 Alina Vdovina

Following Ghomi and Tabachnikov we study topological obstructions to totally skew embeddings of a smooth manifold M in Euclidean spaces. This problem is naturally related to the question of estimating the geometric dimension of the stable…

Algebraic Topology · Mathematics 2010-11-23 Djordje Baralic , Branislav Prvulovic , Gordana Stojanovic , Sinisa Vrecica , Rade Zivaljevic

This paper is the last in a series of three papers which investigate pseudoholomorphic strips in the symplectisation of a three dimensional closed contact manifold with a mixed boundary condition. We will prove a compactness and an…

Symplectic Geometry · Mathematics 2007-05-23 Casim Abbas

We prove some contact analogs of smooth embedding theorems for closed $\pi$-manifolds. We show that a closed, $k$-connected, $\pi$-manifold of dimension (2n + 1) that bounds a $\pi$-manifold, contact embeds in the $(4n-2k+3)$-dimensional…

Symplectic Geometry · Mathematics 2020-05-21 Kuldeep Saha

In this paper, by refining approximation theorems for holomorphic sections of adjoint line bundles, it is proved that the regular locus of a weakly pseudoconvex complex space admitting a positive line bundle can be holomorphically embedded…

Complex Variables · Mathematics 2025-12-30 Yuta Watanabe

This paper aims to study the $(m,\rho)$-quasi Einstein manifold. This article shows that a complete and connected Riemannian manifold under certain conditions becomes compact. Also, we have determined an upper bound of the diameter for such…

Differential Geometry · Mathematics 2022-07-01 Absos Ali Shaikh , Prosenjit Mandal , Chandan Kumar Mondal

We prove that an m-dimensional unit ball D^m in the Euclidean space {\mathbb R}^m cannot be isometrically embedded into a higher-dimensional Euclidean ball B_r^d \subset {\mathbb R}^d of radius r < 1/2 unless one of two conditions is met --…

Mathematical Physics · Physics 2014-07-02 S. C. Venkataramani , T. A. Witten , E. M. Kramer , R. P. Geroch

In this paper we consider the existence and regularity of weakly polyharmonic almost complex structures on a compact almost Hermitian manifold $M^{2m}$. Such objects satisfy the elliptic system weakly $[J, \Delta^m J]=0$. We prove a very…

Differential Geometry · Mathematics 2019-09-24 Weiyong He , Ruiqi Jiang

Almost-complex and hyper-complex manifolds are considered in this paper from the point of view of complex analysis and potential theory. The idea of holomorphic coordinates on an almost-complex manifold $(M,\mathbf{J}%)$ is suggested by D.…

Complex Variables · Mathematics 2007-05-23 S. Dimiev , R. Lazov , N. Milev

In this paper we extend the notion of the Kobayashi-Royden pseudonorm for almost complex manifolds. Its basic properties known from the complex analysis are preserved in the nonintegrable case as well. The main theorem on coincidence of the…

Complex Variables · Mathematics 2007-05-23 B. Kruglikov