5 papers
Thermodynamic Interpretation of the Kompanneets-Chernov-Kantowski-Sachs Solutions
Salvador Mengual, Joan Josep Ferrando
The spatially homogeneous perfect fluid solutions by Kompanneets-Chernov-Kantowski-Sachs are interpreted as a thermodynamic perfect fluid in isentropic evolution, namely, the isent…
Dimension of the isometry group in type N vacuum solutions: an IDEAL approach
Juan Antonio Sáez, Salvador Mengual, Joan Josep Ferrando
The necessary and sufficient conditions for a type N vacuum solution (with cosmological constant) to admit a group of isometries of dimension are given in terms of the invarian…
Obtaining the multiple Debever null directions
Juan Antonio Sáez, Salvador Mengual, Joan Josep Ferrando
The explicit expression of the multiple Debever null directions of an algebraically special spacetime are obtained in terms of the electric and magnetic parts of the Weyl tensor. A…
Spatially-Homogeneous Cosmologies
Juan Antonio Sáez, Salvador Mengual, Joan Josep Ferrando
The necessary and sufficient conditions for a perfect fluid solution to define a spatially-homogeneous cosmology are achieved. These conditions are Intrinsic, Deductive, Explicit a…
Thermodynamics of the universes admitting isotropic radiation
Salvador Mengual, Joan Josep Ferrando, Juan Antonio Sáez
The thermodynamic interpretation of the Stephani Universes is studied in detail. The general expression of the speed of sound and of the thermodynamic schemes associated with a the…