On spherically symmetric perfect-fluid solutions admitting conformal motions

Spherically symmetric perfect-fluid space-times admitting a conformal Killing vector field (CKVF) are discussed. A different coordinate representation of the solutions obtained by Herrera and Kitamura is derived. Exact solutions of Einstein's field equations are found in the case when the conformal Killing vector field is parallel to the 4-velocity vector field u(a). Some physical properties of the obtained solutions are examined. These solutions contain non-vanishing expansion, acceleration and shear. The Ricci collineation symmetries for a spherically symmetric perfect fluid are also investigated. It is found that no such space-times admit the Ricci collineation vector field neither orthogonal nor parallel to the 4-velocity vector field.