Projective symmetry in FRW spacetimes

This paper presents a general discussion of projective symmetry in FRW spacetimes. It is shown that there is at most one proper projective vector field 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.