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Osserman and Conformally Osserman Manifolds with Warped and Twisted Product Structure
We characterize Osserman and conformally Osserman Riemannian manifolds with the local structure of a warped product. By means of this approach we...
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On a Submersion Between Reinhart Lightlike Manifolds and Semi-Riemannian Manifolds
In this paper, we introduce a new submersion, namely, screen lightlike submersion between a lightlike manifold and a semi-Riemannian manifold. We...
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Curvature in Special Base Conformal Warped Products
We introduce the concept of a base conformal warped product of two pseudo-Riemannian manifolds. We also define a subclass of this structure called as...
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A new class of compact spacetimes without closed causal geodesics
We construct the first examples of geodesically complete compact spacetimes admitting a regular globally hyperbolic covering, but which do not...
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Quasi-Kähler Manifolds with a Pair of Norden Metrics
The basic class of the non-integrable almost complex manifolds with a pair of Norden metrics are considered. The interconnections between...
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On the Curvature Groups of a CR Manifold
We show that any contact form whose Fefferman metric admits a nonzero parallel vector field is pseudo-Einstein of constant pseudohermitian scalar...
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Real Lightlike Hypersurfaces of Paraquaternionic Kähler Manifolds
The main purpose of this paper is to give basic properties of real lightlike hypersurfaces of paraquaternionic manifold and to prove the nonexistence...
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The moduli space of embedded singly periodic maximal surfaces with isolated singularities in the Lorentz–Minkowski space \(\mathbb{L}^3\)
We show that, up to some natural normalizations, the moduli space of singly periodic complete embedded maximal surfaces in the Lorentz–Minkowski...
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Minimal surfaces and particles in 3-manifolds
We consider 3-dimensional anti-de Sitter manifolds with conical singularities along time-like lines, which is what in the physics literature is known...
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Conformal vector fields on spacetimes
We study conformal vector fields and their zeros on spacetimes which are non-conformally-flat. Depending on the Petrov type, we classify all...
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Timelike surfaces of constant mean curvature ±1 in anti-de Sitter 3-space ℍ3 1(−1)
It is shown that timelike surfaces of constant mean curvature ± in anti-de Sitter 3-space ℍ 3 1 (−1) can be constructed from a pair of Lorentz...
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Quadratic Bolza Problems in Static Spacetimes with Critical Asymptotic Behavior
The aim of this paper is to investigate the existence of trajectories under the action of an external field in a (standard) static spacetime when...
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On almost complex structures on tangent bundles
Let <InlineEquation ID=IE"1"><EquationSource Format="TEX"><
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Hypersurfaces of the Euclidean sphere with nonnegative Ricci curvature
In this paper we prove that a compact oriented hypersurface of a Euclidean sphere with nonnegative Ricci curvature and infinite fundamental group is...
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Lorentz Geometry of 2-Step Nilpotent Lie Groups
We study the geometry of 2-step nilpotent Lie groups endowed with left-invariant Lorentz metrics. After integrating explicitly the geodesic...
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Uniqueness of Noncompact Spacelike Hypersurfaces of Constant Mean Curvature in Generalized Robertson–Walker Spacetimes
On any spacelike hypersurface of constant mean curvature of a Generalized Robertson–Walker spacetime, the hyperbolic angle θ between the...