95 citations · 625 across the 35 of their papers we have counts for
6 papers · 1 filter
On tilted perfect fluid Bianchi type VI self-similar models
Pantelis S. Apostolopoulos
We show that the tilted perfect fluid Bianchi VI family of self-similar models found by Rosquist and Jantzen [K. Rosquist and R. T. Jantzen, \emph{% Exact power law solutions o…
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…
Self-similar Bianchi type VIII and IX models
Pantelis S. Apostolopoulos, Michael Tsamparlis
It is shown that in transitively self-similar spatially homogeneous tilted perfect fluid models the symmetry vector is not normal to the surfaces of spatial homogeneity. A direct c…
Self-similar Bianchi models: I. Class A models
Pantelis S. Apostolopoulos
We present a study of Bianchi class A tilted cosmological models admitting a proper homothetic vector field together with the restrictions, both at the geometrical and dynamical le…
Note on Matter Collineations in Kantowski-Sachs, Bianchi Types I and III Spacetimes
Pantelis S. Apostolopoulos, Michael Tsamparlis
We show that the classification of Kantowski-Sachs, Bianchi Types I and III spacetimes admitting Matter Collineations (MCs) presented in a recent paper by Camci et al. [Camci, U.,…