4 papers · 1 filter
Lie and Noether symmetries of geodesic equations and collineations
Michael Tsamparlis, Andronikos Paliathanasis
The Lie symmetries of the geodesic equations in a Riemannian space are computed in terms of the special projective group and its degenerates (affine vectors, homothetic vector and…
Ricci and matter collineations of locally rotationally symmetric space-times
Michael Tsamparlis, Pantelis S. Apostolopoulos
A new method is presented for the determination of Ricci Collineations (RC) and Matter Collineations (MC) of a given spacetime, in the cases where the Ricci tensor and the energy m…
Geometric equations of state in Friedmann-Lemaître universes admitting matter and Ricci Collineations
Pantelis S. Apostolopoulos, Michael Tsamparlis
As a rule in General Relativity the spacetime metric fixes the Einstein tensor and through the Field Equations (FE) the energy-momentum tensor. However one cannot write the FE expl…
Ricci and Matter inheritance collineations of Robertson-Walker space-times
Pantelis S. Apostolopoulos, Michael Tsamparlis
It is well known that every Killing vector is a Ricci and Matter collineation. Therefore the metric, the Ricci tensor and the energy-momentum tensor are all members of a large fami…