Astronomy and Astrophysics – Astrophysics – General Relativity and Quantum Cosmology
Scientific paper
2003-09-04
Gen.Rel.Grav. 36 (2004) 277-292
Astronomy and Astrophysics
Astrophysics
General Relativity and Quantum Cosmology
14 pages, Latex; to appear in General Relativity and Gravitation
Scientific paper
10.1023/B:GERG.0000010475.20566.
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 explicitly until a class of observers has been considered. Every class of observers defines a decomposition of the energy-momentum tensor in terms of the dynamical variables energy density ($\mu$), the isotropic pressure ($p$), the heat flux $q^a$ and the traceless anisotropic pressure tensor $\pi_{ab}$. The solution of the FE requires additional assumptions among the dynamical variables known with the generic name equations of state. These imply that the properties of the matter for a given class of observers depends not only on the energy-momentum tensor but on extra a priori assumptions which are relevant to that particular class of observers. This makes difficult the comparison of the Physics observed by different classes of observers for the {\it same} spacetime metric. One way to overcome this unsatisfactory situation is to define the extra condition required among the dynamical variables by a geometric condition, which will be based on the metric and not to the observers. Among the possible and multiple conditions one could use the consideration of collineations. We examine this possibility for the Friedmann-Lema\^{i}tre-Robertson-Walker models admitting matter and Ricci collineations and determine the equations of state for the comoving observers. We find linear and non-linear equations of state, which lead to solutions satisfying the energy conditions, therefore describing physically viable cosmological models.
Apostolopoulos Pantelis S.
Tsamparlis Michael
No associations
LandOfFree
Geometric equations of state in Friedmann-Lemaître universes admitting matter and Ricci Collineations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Geometric equations of state in Friedmann-Lemaître universes admitting matter and Ricci Collineations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Geometric equations of state in Friedmann-Lemaître universes admitting matter and Ricci Collineations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-56986