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In this paper, we study the geometry of a connected oriented cmc Riemannian hypersurface $M$ of a semi-Riemannian group $G$ of Lie algebra $\mathfrak g$ and index 0 or 1. If $G$ is Riemannian and $M$ is compact and transversal to an element…

Differential Geometry · Mathematics 2014-01-03 Antonio Caminha

By a classical theorem of Gallot (1979), a Riemannian cone over a complete Riemannian manifold is either flat or has irreducible holonomy. We consider metric cones with reducible holonomy over pseudo-Riemannian manifolds. First we describe…

Differential Geometry · Mathematics 2012-08-14 D. V. Alekseevsky , V. Cortés , A. Galaev , T. Leistner

We prove the existence of solutions of the cohomological equation for the geodesic flow on the unit tangent bundle of a compact flat surface with finitely many cone points. We also prove the ergodicity of the holonomy foliation for surfaces…

Dynamical Systems · Mathematics 2025-10-22 Giovanni Forni , Nelson Moll

We introduce conformal anti-invariant submersions from almost Hermitian manifolds onto Riemannian manifolds. We give examples, investigate the geometry of foliations which are arisen from the definition of a conformal submersion and find…

Differential Geometry · Mathematics 2015-04-23 Mehmet Akif Akyol , Bayram Sahin

Real world data often lie on low-dimensional Riemannian manifolds embedded in high-dimensional spaces. This motivates learning degenerate normalizing flows that map between the ambient space and a low-dimensional latent space. However, if…

Machine Learning · Computer Science 2026-04-14 Hanlin Yu , Søren Hauberg , Marcelo Hartmann , Arto Klami , Georgios Arvanitidis

We prove the integrability of geodesic flows on the Riemannian g.o. spaces of compact Lie groups, as well as on a related class of Riemannian homogeneous spaces having an additional principal bundle structure.

Differential Geometry · Mathematics 2012-07-05 Bozidar Jovanovic

We introduce slant Riemannian maps from Riemannian manifolds to almost Hermitian manifolds as a generalization of slant immersions, invariant Riemannian maps and anti-invariant Riemannian maps. We give examples, obtain characterizations and…

Differential Geometry · Mathematics 2012-06-18 Bayram Sahin

We study the full holonomy group of Lorentzian manifolds with a parallel null line bundle. We prove several results that are based on the classification of the restricted holonomy groups of such manifolds and provide a construction method…

Differential Geometry · Mathematics 2014-09-18 Helga Baum , Kordian Lärz , Thomas Leistner

We develop a general structure theory for compact homogeneous Riemannian manifolds in relation to the co-index of symmetry. We will then use these results to classify irreducible, simply connected, compact homogeneous Riemannian manifolds…

Differential Geometry · Mathematics 2013-12-23 Jurgen Berndt , Carlos Olmos , Silvio Reggiani

A singular riemannian foliation on a complete riemannian manifold is said to be riemannian if each geodesic that is perpendicular at one point to a leaf remains perpendicular to every leaf it meets. The singular foliation is said to admit…

Differential Geometry · Mathematics 2007-05-23 Marcos M. Alexandrino , Dirk Toeben

This is the first part of a series on non-compact groups acting isometrically on compact Lorentz manifolds. This subject was recently investigated by many authors. In the present part we investigate the dynamics of affine, and especially…

dg-ga · Mathematics 2007-05-23 Abdelghani Zeghib

The notion of being totally umbilic is considered for non-degenerate and degenerate submanifolds of semi-Riemanian manifolds. After some remarks on the general case, timelike and lightlike totally umbilic submanifolds of Lorentzian…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Volker Perlick

Recently, classical results on completeness of trajectories of Hamiltonian systems obtained at the beginning of the seventies, have been revisited, improved and applied to Lorentzian Geometry. Our aim here is threefold: to give explicit…

Differential Geometry · Mathematics 2013-04-18 Anna Maria Candela , Alfonso Romero , Miguel Sánchez

In this paper, we study the topology of complete noncompact Riemannian manifolds with asymptotically nonnegative Ricci curvature. We show that a complete noncompact manifold with asymptoticaly nonnegative Ricci curvature and sectional…

Differential Geometry · Mathematics 2008-09-29 Bazanfare Mahaman

We use functions of a bicomplex variable to unify the existing constructions of harmonic morphisms from a 3-dimensional Euclidean or pseudo-Euclidean space to a Riemannian or Lorentzian surface. This is done by using the notion of…

Differential Geometry · Mathematics 2010-03-12 Paul Baird , John C. Wood

This is an intuitive survey of extrinsic and intrinsic notions of convergence of manifolds complete with pictures of key examples and a discussion of the properties associated with each notion. We begin with a description of three extrinsic…

Differential Geometry · Mathematics 2013-04-08 Christina Sormani

By studying spaces of flow graphs in a closed oriented manifold, we construct operations on its cohomology, parametrized by the homology of the moduli spaces of compact Riemann surfaces with boundary marked points. We show that the…

Geometric Topology · Mathematics 2013-05-03 Viktor Fromm

We propose a new approach to the study of compact Riemannian manifolds with nonnegative Ricci curvature and strictly convex boundary or positive Ricci curvature and convex boundary. Several conjectures are formulated. Some partial results…

Differential Geometry · Mathematics 2020-05-27 Xiaodong Wang

On a Lorentzian manifold the existence of a parallel null vector field implies certain constraint conditions on the induced Riemannian geometry of a space-like hypersurface. We will derive these constraint conditions and, conversely, show…

Differential Geometry · Mathematics 2022-04-14 Helga Baum , Thomas Leistner , Andree Lischewski

We contribute to an original problem studied by Hamilton and others, in order to understand the behaviour of maximal solutions of the Ricci flow both in compact and non-compact complete orientable Riemannian manifolds of finite volume. The…

Differential Geometry · Mathematics 2023-11-21 Stefano Nardulli , Francesco G. Russo