Projective symmetry in FRW spacetimes

This paper presents a general discussion of projective symmetry in FRW spac etimes. It is shown that there is at most one proper projective vector fiel d admitted in the sense that any other projective vector field is a linear combination of the original and a homothetic vector field. The situation is , essentially, solved completely for the FRW models with k = +/-1 and up to quadratures in the case k = 0.