The local structure of essentially conformally symmetric manifolds with constant fundamental function I. The elliptic case
The local structure of essentially conformally symmetric manifolds with constant fundamental function. III. The parabolic case
The metrics of a twodimensional space with geodesics represented by a linear equation
The nonexistence of rank 4 IP tensors in signature .
The Plane-Time in Which Paths of Inertional Motions Are Conics
The Projectivization of Conformal Models of Fibrations Determined by the Algebra of Quaternions
Our aim is to study the principal bundles determined by the algebra of quaternions in the projective model. The projectivization of the conformal model of the Hopf fibration is considered as example.
The structure of reachable sets for affine control systems induced by generalized Martinet sub-lorentzian metrics
In this paper we investigate analytic affine control systems q̇ = X + uY, u ∈ [a,b] , where X,Y is an orthonormal frame for a generalized Martinet sub-Lorentzian structure of order k of Hamiltonian type. We construct normal forms for such systems and, among other things, we study the connection between the presence of the singular trajectory starting at q0 on the boundary of the reachable set from q0 with the minimal number of analytic functions needed for describing the reachable set from q0.
Theorems concerning certain special tensor fields on Riemannian manifolds and their applications.
Three dimensional near-horizon metrics that are Einstein-Weyl
We investigate which three dimensional near-horizon metrics admit a compatible 1-form such that defines an Einstein-Weyl structure. We find explicit examples and see that some of the solutions give rise to Einstein-Weyl structures of dispersionless KP type and dispersionless Hirota (aka hyperCR) type.
Timelike -slant helices in Minkowski space
We consider a unit speed timelike curve in Minkowski 4-space and denote the Frenet frame of by . We say that is a generalized helix if one of the unit vector fields of the Frenet frame has constant scalar product with a fixed direction of . In this work we study those helices where the function is constant and we give different characterizations of such curves.
Timelike quaternion frame of a non-lightlike curve.
Total absolute curvature of curves in Lorentz Manifolds
Totally umbilical submanifolds in some semi-Riemannian manifolds
We investigate totally umbilical submanifolds in manifolds satisfying some curvature conditions of either recurrent or pseudosymmetry type in the sense of Ryszard Deszcz and derive the respective condition for submanifolds. We also prove some relations involving the mean curvature and the Weyl conformal curvature tensor of submanifolds. Some examples are discussed.
Two-jets of conformal fields along their zero sets
The connected components of the zero set of any conformal vector field v, in a pseudo-Riemannian manifold (M, g) of arbitrary signature, are of two types, which may be called ‘essential’ and ‘nonessential’. The former consist of points at which v is essential, that is, cannot be turned into a Killing field by a local conformal change of the metric. In a component of the latter type, points at which v is nonessential form a relatively-open dense subset that is at the same time a totally umbilical...
Une perturbation à symétrie sphérique de la métrique d'un univers en expansion
Values of pseudoriemannian sectional cuvature.
Variétés spatiales de codimension deux immergées dans un espace de Minkowski muni d'une connexion principale
Vector fields generating certain special transformations
Zur Linearität 2-dimensionaler Raum-Zeit-Transformationen.
-Ricci Solitons on -Einstein -Manifolds
The object of the present paper is to study -Ricci solitons on -Einstein -manifolds. It is shown that if is a recurrent torse forming -Ricci soliton on an -Einstein -manifold then is (i) concurrent and (ii) Killing vector field.