CRITICAL PHENOMENA AND SELF-SIMILARITY IN THE GRAVITATIONAL COLLAPSE OF RADIATION FLUID

We observe critical phenomena in spherical collapse of radiation fluid. A sequence of spacetimes S[eta] is numerically computed, containing models (eta much less than 1) that adiabatically disperse and models (eta much greater than 1) that form a black hole. Near the critical point (eta(c)), evolutions develop a self-similar region within which collapse is balanced by a strong, inward-moving rarefraction wave that holds m(r)/r constant as a function of a self-similar coordinate xi. The self-similar solution is known and we show near-critical evolutions asymptotically approaching it. A critical exponent beta congruent-to 0.36 is found for supercritical (eta > eta(c)) models.