Results 41 to 50 of about 464 (128)

Conformal Isometries and Curvature Collineations of an Impulsive Plane Wave: a distributional approach

, 2021
By extending the notion of Lie derivative to distribution-valued tensor fields of order $m$, Lie derivatives with respect to $C^k$ vector fields, $k\geqslant m+1$, can be shown to be well defined. Geometric symmetries, definable in terms of these Lie derivatives, can then be considered.
Calles, Juan, Pantoja, Nelson
openaire   +2 more sources

Conformal Ricci collineations of static spherically symmetric spacetimes

, 2010
Conformal Ricci collineations of static spherically symmetric spacetimes are studied. The general form of the vector fields generating conformal Ricci collineations is found when the Ricci tensor is non-degenerate, in which case the number of independent
Asghar Qadir, Bokhari A H, Camci U, Duggal K L, K Saifullah, Keane A J, Maartens R, Qadir A, Stephani H, Ugur Camci, Ziad M   +10 more
core   +1 more source

Stereo image processing system for robot vision [PDF]

, 2009
More and more applications (path planning, collision avoidance methods) require 3D description of the surround world. This paper describes a stereo vision system that uses 2D (grayscale or color) images to extract simple 2D geometric entities (points,
Lantos, Béla, Tél, Ferenc
core  

Symmetries of distributional domain wall geometries

, 2003
Generalizing the Lie derivative of smooth tensor fields to distribution-valued tensors, we examine the Killing symmetries and the collineations of the curvature tensors of some distributional domain wall geometries.
Alberto Sanoja, Choquet-Bruhat Y., Choquet-Bruhat Y., Lichnerowicz A., Nelson Pantoja   +4 more
core   +1 more source

Study of the Magnitude-Redshift Relation for type Ia Supernovae in a Model resulting from a Ricci-Symmetry

, 2001
Models with a dynamic cosmological term \Lambda (t) are becoming popular as they solve the cosmological constant problem in a natural way. Instead of considering any ad-hoc assumption for the variation of \Lambda, we consider a particular symmetry, the ...
Vishwakarma, R. G.
core   +2 more sources

On the general structure of Ricci collineations for type B warped spacetimes

, 2004
A complete study of the structure of Ricci collineations for type B warped spacetimes is carried out. This study can be used as a method to obtain these symetries in such spacetimes.
Apostolopoulos P. S., Camci U., Carot J., Carot J., Carot J., Hall G. S., Hall G. S., J. L. Flores, Katzin G. H., U. Percoco, Y. Parra   +10 more
core   +1 more source

Semiconformal symmetry- A new symmetry of the spacetime manifold of the general relativity

, 2019
In this paper we have introduced a new symmetry property of spacetime which is named as semiconformal curvature collineation, and its relationship with other known symmetry properties has been established.
Ahsan, Zafar, Ali, Musavvir, Pundeer, Naeem Ahmad   +2 more
core  

On the definition of matter collineations

, 2010
It is shown that when the stress-energy tensor of a spacetime is diagonal and is written in the mixed form, its collineations admit infinite dimensional Lie algebras except possibly in the case when the tensor depends on all the spacetime coordinates ...
ASGHAR QADIR, K. SAIFULLAH, Misner C. W., Penrose R., Saifullah K.   +4 more
core   +1 more source

Two dimensional dynamical systems which admit Lie and Noether symmetries

, 2011
We prove two theorems which relate the Lie point symmetries and the Noether symmetries of a dynamical system moving in a Riemannian space with the special projective group and the homothetic group of the space respectively.
Aminova A V, Aminova A V, Andronikos Paliathanasis, Athorne C, Cervero J M, Kehagias A, Leach P G L, Lutzky M, Michael Tsamparlis, Moyo S, Olver P J, Prince G E, Stephani H   +12 more
core   +1 more source

About Bianchi I with VSL

, 2008
In this paper we study how to attack, through different techniques, a perfect fluid Bianchi I model with variable G,c and Lambda, but taking into account the effects of a $c$-variable into the curvature tensor. We study the model under the assumption,div(
A. Albrecht, A. Beesham, A. Beesham, A. Einstein, A. Harvey, A. Pradhan, A. Pradhan, A. Pradhan, A. Pradhan, A.-M.M. Abdel-Rahman, A.-M.M. Abdel-Rahman, A.A. Coley, A.I. Arbab, A.K. Raychaudhuri, A.M. Sintes, A.Z. Petrov, B. Carter, B. Carter, B. Saha, B. Saha, B.A. Bassett, B.J. Cantwell, B.J. Carr, C.B. Collins, C.P. Singh, D. Kalligas, D.M. Eardley, E. Kasner, E.R. Harrison, G.F.R. Ellis, G.I. Barenblatt, G.S. Hall, G.S. Hall, G.W. Bluman, H. Maeda, H. Stephani, I. Waga, İ. Yavuz, J. Caminati, J. Carot, J. Carot, J. Magueijo, J. Wainwright, J. Wainwright, J.A. Belinchón, J.A. Belinchón, J.A. Belinchón, J.A.S. Lima, J.A.S. Lima, J.C. Carvalho, J.D. Barrow, J.D. Barrow, J.W. Moffat, José Antonio Belinchón, K. Rosquits, K. Rosquits, K.L. Duggal, L. Hsu, M. Sharif, M. Sharif, M. Sharif, M. Szydlowski, M. Tsamparlis, M. Tsamparlis, M.A.H. MacCallum, M.E. Cahill, M.P. Ryan, M.S. Berman, N.H. Ibragimov, P.A.M. Dirac, P.J.E. Peebles, P.M. Benoit, P.P. Avelino, P.T. Olver, R.F. Sistero, T. Harko, T. Padmanabhan, T. Padmanabhan, T. Singh, U. Camcı, U. Camcı, V. Sahni, W. Chen, Y.K. Lau, Y.K. Lau   +84 more
core   +1 more source