TIMELIKE AND SPACELIKE MATTER INHERITANCE VECTORS IN SPECIFIC FORMS OF ENERGY–MOMENTUM TENSOR

This paper is devoted to the investigation of the consequences of timelike and spacelike matter inheritance vectors in specific forms of energy–momentum tensor, i.e. for string cosmology (string cloud and string fluid) and perfect fluid. Necessary and sufficient conditions are developed for a space–time with string cosmology and perfect fluid to admit a timelike matter inheritance vector, parallel to ua and spacelike matter inheritance vector, parallel to xa. We compare the outcome with the conditions of conformal Killing vectors. This comparison provides us the conditions for the existence of matter inheritance vector when it is also a conformal Killing vector. Finally, we discuss these results for the existence of matter inheritance vector in the special cases of the above mentioned space–times.