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We give an easy example showing that sections of a singular Riemannian foliation on a simply connected space neither have to be isometric nor injectively immersed.

Differential Geometry · Mathematics 2013-10-04 Stephan Wiesendorf

Some curvature estimates are derived from geometrical data concerning quasi-conformality properties of some commuting linearly independent vector fields on a compact Riemannian manifold.

dg-ga · Mathematics 2008-02-03 Pawel Walczak

This paper is a continuation of our investigation of the anisotropic conformal change of a conic pseudo-Finsler surface $(M,F)$, namely, the change $\overline{F}(x,y)=e^{\phi(x,y)}F(x,y)$ \cite{first paper}. We obtain the relationship…

Differential Geometry · Mathematics 2025-03-12 Nabil L. Youssef , S. G. Elgendi , A. A. Kotb , Ebtsam H. Taha

In this paper, we establish a number of results about the topology of the leaves of a closed singular Riemannian foliation $(M,\fol)$. If $M$ is simply connected, we prove that the leaves are finitely covered by nilpotent spaces, and…

Differential Geometry · Mathematics 2022-04-01 Marco Radeschi , Elahe Khalili Samani

In this note, we prove that for a complete noncompact three dimensional Riemannian manifold with bounded sectional curvature, if it has uniformly positive scalar curvature, then there is a uniform lower bound on the injectivity radius.

Differential Geometry · Mathematics 2023-02-24 Conghan Dong

Given a manifold (or, more generally, a developable orbifold) $M_0$ and two closed Riemannian manifolds $M_1$ and $M_2$ with a finite covering map to $M_0$, we give a spectral characterisation of when they are equivalent Riemannian covers…

Differential Geometry · Mathematics 2021-07-02 Gunther Cornelissen , Norbert Peyerimhoff

Explicit representations of complex structures on closed manifolds are valuable, but relatively rare in the literature. Using isoparametric theory, we construct complex structures on isoparametric hypersurfaces with $g=4, m=1$ in the unit…

Differential Geometry · Mathematics 2025-02-14 Chao Qian , Zizhou Tang , Wenjiao Yan

In this paper we give bounds for the first eigenvalue of the conformal Laplacian and the Yamabe invariant of a compact Riemannian manifold, by using conditions on the Ricci curvature and the diameter and deduce certain conditions on the…

Differential Geometry · Mathematics 2008-04-23 Salem Eljazi , Najoua Gamara , Habiba Guemri

We show that complete conformally flat manifolds of dimension n>2 with nonnegative Ricci curvature enjoy nice rigidity properties: they are either flat, or locally isometric to a product of a sphere and a line, or are globally conformally…

Differential Geometry · Mathematics 2007-05-23 Gilles Carron , Marc Herzlich

We study the conditions under which the tangent bundle $(TM,G)$ of an $n$-dimensional Riemannian manifold $(M,g)$ is conformally flat, where $G$ is a general natural lifted metric of $g$. We prove that the base manifold must have constant…

Differential Geometry · Mathematics 2008-10-10 S. L. Druta

We establish normal forms for conformal vector fields on pseudo-Riemannian manifolds in the neighborhood of a singularity. For real-analytic Lorentzian manifolds, we show that the vector field is analytically linearizable or the manifold is…

Differential Geometry · Mathematics 2012-09-19 Charles Frances , Karin Melnick

Irreducible isoparametric foliations of arbitrary codimension q on complex projective spaces CP^n are classified, except if n=15 and q=1. Remarkably, there are noncongruent examples that pull back under the Hopf map to congruent foliations…

Differential Geometry · Mathematics 2014-03-05 Miguel Dominguez-Vazquez

Among a family of 2-parameter left invariant metrics on Sp(2), we determine which have nonnegative sectional curvatures and which are Einstein. On the quotiente $\widetilde{N}^{11}=(Sp(2)\times S^4)/S^3$, we construct a homogeneous…

Differential Geometry · Mathematics 2020-04-29 Chao Qian , Zizhou Tang , Wenjiao Yan

We study conformal bi-slant submersions from almost Hermitian manifolds onto Riemannian manifolds as a generalized of conformal anti-invariant, conformal semi-invariant, conformal semi-slant, conformal slant and conformal hemi-slant…

General Mathematics · Mathematics 2020-10-01 Sezin Aykurt Sepet

We discuss the analogy between collapsing Conformal Field Theories and measured Gromov-Hausdorff limit of Riemannian manifolds with non-negative Ricci curvature. Motivated by this analogy we propose the notion of non-commutative…

High Energy Physics - Theory · Physics 2025-06-03 Yan Soibelman

We show any Riemannian curvature model can be geometrically realized by a manifold with constant scalar curvature. We also show that any pseudo-Hermitian curvature model, para-Hermitian curvature model, hyper-pseudo-Hermitian curvature…

Differential Geometry · Mathematics 2008-11-12 M. Brozos-Vazquez , P. Gilkey , H. Kang , S. Nikcevic , G. Weingart

Let M be a complete Riemannian manifold whose sectional curvature is bounded above by 1. We say that M has positive spherical rank if along every geodesic one hits a conjugate point at t=\pi. The following theorem is then proved: If M is a…

Differential Geometry · Mathematics 2007-05-23 Krishnan Shankar , Ralf Spatzier , Burkhard Wilking

Let M be a compact Riemannian manifold without boundary and let E be a Riemannian vector bundle over M. If $\sigma$ denotes the sphere subbundle of E, we look for embeddings of $\sigma$ into E admitting a prescribed mean curvature.

Differential Geometry · Mathematics 2016-01-25 Pascal Cherrier , Abdellah Hanani

We study in spherical symmetry the conformal compactification for hyperboloidal foliations with nonvanishing constant mean curvature. The conformal factor and the coordinates are chosen such that null infinity is at a fixed radial…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Anil Zenginoglu , Sascha Husa

For a Riemannian covering $\pi\colon M_1\to M_0$, the bottoms of the spectra of $M_0$ and $M_1$ coincide if the covering is amenable. The converse implication does not always hold. Assuming completeness and a lower bound on the Ricci…

Differential Geometry · Mathematics 2021-03-09 Werner Ballmann , Henrik Matthiesen , Panagiotis Polymerakis