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 is numerically computed, containing models (1) that adiabatically disperse and models (1) that form a black hole. Near the critical point (₂), evolutions develop a self-similar region within which collapse is balanced by a strong, inward-moving rarefaction wave that holds m (r) /r constant as a function of a self-similar coordinate. The self-similar solution is known and we show near-critical evolutions asymptotically approaching it. A critical exponent 0. 36 is found for supercritical (>₂) models.