Critical behavior in gravitational collapse of a perfect fluid

To confirm the scenario of critical behavior in gravitational collapse in a previous paper we carry out a rather complete analysis for perfect fluids with pressure proportional to density, in a wide range of the adiabatic index gamma. In particular, the uniqueness of the relevant mode around a fixed point is established by a Lyapunov analysis. This shows that critical phenomena occur not only for the radiation fluid but also for perfect fluids with 1 < gamma less than or similar to 1.889. We also analyze the stability of other self-similar solutions and also discuss the universality class. [S0556-2821(98)04324-0].